Let's begin by first creating a simple background for our first room. Since we are planning later to cover using Doors, we may as well make an inside room.
Begin by Selecting a visual color of black and the line tool. You may also find it useful to go ahead and place the fake ego on the screen, this will help you immeasurably in getting the size relationships correct. If you aren't sure how to do any of these things, you may really want to take a moment and read about the Pic Editor in the Getting Started tutorial group and then coming back.
Lets begin by outlining the door by drawing three lines.
From coordinates (191, 112) to (191, 64) which will be the left edge
From coordinates (191, 64) to (228, 64) which is the top edge
From coordinates (228, 64) to (228, 112) which is the right edge
With that done, now just go ahead and trace out the remainder of your rooms walls however it is that you see fit. This is what I came up with. So far, everything has been done in the visual screen and I still have the fake ego showing to show the size relationship with the doorway.
Now, let's go ahead and take care of creating the initial control lines. The white control lines, by default, are uncrossable by the ego or other actors. They usually serve to create the room boundaries or other drawn items that ego can not walk over. The easiest way to accomplish this would have been to turn the control colors on and off while we were drawing our room as we can draw on all three screens with a single line. When adding them or updating them to a room pic after it has been drawn however really isn't all that difficult. First while viewing the visual screen, go to edit and select copy, then reselect edit and hit paste. This will place a copy of our visual screen as a tracing image. Now, cycling through the control and priority screens you will see that you can still see our original room. Now simply select the white control color, and trace out the base of our walls.
Now with the basic boundaries and room drawn, the only thing that we have left to cover with the picture editor are the priorities. Priority colors are used to turn our two dimensional image into a three dimensional one such that the ego can walk in front of and behind objects. In our current room, assuming you drew it at least halfway like I did, we currently have two areas that we will need to add priority colors to. The top of the doorway will need to be addressed as well as the frame that I placed around the room as I put the control lines such that the ego can walk just beyond the edges of the framing.
Using the priority bands to determine the priority of the ego, determine the best priority colors to use. The Ego's priority is higher at the bottom of the screen and lowest at the top. After you place a priority color, you can use the fake ego option to test how it will actually work in game. Above the door the Dark Gray color was the best option. Depending on how and where you placed your lines, these colors may vary slightly, but again, that is where the priority bands come into play in help you determine the appropriate color to use.
Save your pic, hit rebuild, and run your game to see your background image in action.