You could compare them with ADL/PreAGI I guess.
I had a look at the ADL and pre-AGI picture formats last night, by looking over the code in scummvm. So the ADL picture format is quite different. The drawing actions are within the 0xE0 range, and it does have the standard four drawing actions, i.e. the X/Y "corner" actions, and the absolute and relative line actions, and also the fill, but as codes in the 0xE0 range. So those drawing actions have been around for a while, but have been shifted around over time. The ADL picture format uses the 0xF0 range for setting different colours, i.e. different codes for different "colours". This is going back to the Apple II days where Ken Williams was the main programmer of the picture editor, and the colours were kind of faked. Sierra published two different picture tools that I'm aware of that were both supposedly the ones that they used for these ADL games. The first was the "Paddle/Tablet Graphics" tool (I think the paddle bit might be where the X/Y "corner" action originated). This tool they were selling back in 1980, shortly after Mystery House was released. Then a few years later, they started selling "The Artist", which was once again claimed to be the tool that they were using internally, but packaged for the general public to purchase.
Looking now at the pre-AGI games:
The scummvm default picture version is the AGIV2 picture format, which is used by the Mickey and Winnie "pre-AGI" Disney games as well, and also the AGIV1 games (KQ2 and BC). Troll's Tale uses what scummvm calls the V1.5 picture format. The scummvm picture class also appears to support a "V1" picture format, but it doesn't look like it is used at present. The AGIV1 games such as KQ2 and BC that came out between KQ and the first AGIV2 games were already using the "AGIV2" picture format.
Looking at the implementation code for the various picture formats supported by scummvm, none of them is an exact match for what I'm seeing in the original King's Quest game. Instead what I'm seeing is a combination of the codes used in the V1, V1.5 and V2 scummvm picture formats. Specifically, it contains all of the picture code actions (0xF1, 0xF3, 0xFA and 0xFB) listed in the switch statement for the drawPictureV1 method (this is the one that I can't see any usage of, so might be a work in progress and therefore incomplete), and the 0xF8, 0xF9, 0xFA, 0xFB and 0xFE codes from the drawPictureV15 method (used by Troll's Tale), and the 0xF4, 0xF5, 0xF6, 0xF7 and 0xFC code from the drawPictureV2 method (I didn't even know that 0xFC was a code in AGIV2; it must be one of the pre-AGI games that uses this). In addition to this, it includes codes that none of the V1, V15 or V2 formats have a matching implementation for, i.e. 0xF0, 0xF2 and 0xFD.
Troll's Tale seems the closest, and it might be the case that this game doesn't use all of the codes, and thus why the scummvm implementation doesn't provide implementations for all of them. I would guess that the Troll's Tale engine is using essentially the same picture format as the booter versions of King's Quest, which hints at the placement of Troll's Tale within the evolution of the AGI picture format.
Likewise, the use of the AGIV1/2 picture format by the Mickey and Winnie games is very interesting. These two games were released at the end of 1984. King's Quest was released in May 1984. Development work on the Mickey and Winnie games probably started mid 1984. - Here's the interesting thing: Someone redesigned the picture editor created by the King's Quest project team in between the the KQ project and the release of the Disney games, and they did so within a quick enough timeframe that the artists working on Mickey and Winnie could use the new version. And that new version was what was subsequently used for the AGIV1 games, i.e. King's Quest II and Black Cauldron, and then also for the AGIV2 games.
My guess, a fairly safe guess I would say, is that this person was Bob Heitman. I will have to ask him this to see if he recalls. He must have done this in mid 1984. He has previously said that he inherited the picture editor built by the KQ team, but that it was from a maintenance perspective rather than building any new features in it. The question is whether this redesign/rearrangement of the picture codes qualifies as maintenance.
Regarding Troll's Tale, scummvm only has game definitions for the PC versions. I suspect that there must have been a project within Sierra to port the game to the PC, and at the time when they did this, the King's Quest picture editor was available for use, but perhaps not the new version that was redesigned for the Mickey and Winnie Disney games. The PC Booter version apparently came out in 1984:
https://www.mobygames.com/game/7271/trolls-tale/credits/pc-booter/And Doug MacNeill (of King's Quest project team fame) did the graphics for it, and Peter Oliphant (of The Dick van Dyke TV show fame) did the programming conversion. Doug must have been quite busy in 1984, because he was also working on the Disney games. I think this places the Troll's Tale PC Booter conversion as taking place between the King's Quest project and the Disney games, since Doug was using the KQ picture editor (apparently built primarily by Ken MacNeill, according to quotes from Doug in Shawn Mills' "The Sierra Adventure" book) for Troll's Tale, but was using the revamped AGIV1/2 picture editor for the Mickey and Winnie Disney games. - I've just checked the Troll's Tale disk image for timestamps, and it looks like the LOAD directory entry has a 5th April 1984 timestamp, which is older than the LOAD timestamps in the first KQ releases. That suggests that the Troll's Tale PC conversation was being worked on prior to the KQ release, but probably after the bulk of the KQ code was written. It makes sense then that Troll's Tale uses the KQ/GAL picture format.
Incidentally, Greg Rowland was involved in converting the "Dragon's Keep" pictures for the PC version in 1984, probably also after the graphics work for the KQ project was complete, with the programming conversion also being done by Peter Oliphant:
https://www.mobygames.com/game/20644/dragons-keep/credits/pc-booter/Peter was another one that was very busy in 1984, as he was the main programmer for Mickey's Space Adventure. So, Peter was working with Doug on the Troll's Tale conversion to the PC, and with Greg on the Dragon's Keep conversion to the PC. My guess is that Dragon's Keep also uses the KQ/GAL picture format then. I'd like to verify that, but the PC version of Dragon's Keep seems rare. Has anyone seen that one anywhere?
(it being rare might be why it isn't supported by scummvm)
Hmmm, now that I'm looking more closely at the specific picture codes of the King's Quest GAL picture format that Troll's Tale is using, it appears to be specifically the visual ones. All of the priority related codes have been avoided. 0xF1 is specifically for setting only the visual colour. 0xFE is for filling in only the visual colour. The codes 0xF8, 0xF9, 0xFA and 0xFB appear to be visual only versions of the more familiar 0xF4, 0xF5, 0xF6 and 0xF7 that draw to both visual and priority. This makes a lot of sense, because Troll's Tale does not have a priority screen. The original game was built in 1983, then ported to the PC, with the pictures being converted to the KQ/GAL picture format. There would be no need for codes that used the priority screen.
Anyway... very long story short, I think I can use some of what I've found in the scummvm source to validate what I've prototyped.