Hello Ian! In principle: yes. The code reverts to a default nation specific bitmap if unit specific is not found. At the moment those are the map snippets with the nation's flag in it.
Off my head I am not sure about the maximum size, maybe that is it. I'll check when I get home. (I have 250x125 popping up from my head, but maybe that's the max size of Scenario Pictures.)
Also I can't recall from top of my head if the Unit Picture needs to be the same as the Unit Bitmap and not Unit ID (in your sample: maybe Up260016, maybe one under another SP size), as often there's several entries for same unit type but with different Strength. I'll check that too later.
EDIT: See HERE. By Unit Bitmap I refer to parameter #20, in the sample see how the two SA-6 platoons have the same parameter value there: despite of the two entries of two sized, they are represented by the same Unit Image 3D bitmap file. In case of SA-6, both Unit ID P238009 (Strength: 4 platforms) and Unit ID P238010 (Strength: 2 platforms) use P238009.bmp.
One thing about the bitmaps: they need to be on a 256 color mode, make sure you save them in that manner. They need not be black and white, they can be color too, as long they're stored in 256 color mode.
And: they need to be saved under \Pictures folder.
I'll get back to you, would be cool to have a User Mod with Unit Pictures.
< Message edited by Crossroads -- 3/13/2017 11:09:01 AM >