I just figured out how to do it a day ago! Here's how it works.
(Copypaste from tutorial i saved)
6) Adding your own console background for the console menu
This is also a little different as far as the method goes, though I don't think it's nearly as hard as creating a custom logo. Again, this step is purely optional, but if you're interested, here's how you do it:
The console is noting but a regular old bitmap file. However, this bitmap file will have to be compiled into a file called cached.wad. As far as I understand it, the reason for this is, that because this is rendered as 3D, rather than a 2D splash (remember, that the console background is often accessed in-game), then the image is treated like a texture. Although I still can't exactly figure out why images can't be opened up in wad editors like Wally. So on that note, we'll have to compile that stupid wad file manually. Don't worry, it's straightforward. Make your bitmap image at 320x200. This file has to be saved as an 8-bit 256 color BMP (qlumpy won't accept 16-bit). It doesn't really matter what you name it when you save it. I'd just name it console.bmp. Now you'll need a file called qlumpy.exe to compile it. This file is included in the Full SDK (not sure about the light SDK). If you don't have the SDK, I suggest you download it.
Now we'll make a new empty directory. For the example, just follow along with me. Once you've done it, you can go ahead and make changes or do it in different directories. Make a directory on you C: drive called console. So now you have C:console (obviously). Now copy your console.bmp file and qlumpy.exe file into c:console. Now for the fun part; we have to make scripting instructions, kind of like a liblist file. Don't panic though, it's simple enough. Open Wordpad (Yes, just Wordpad. That's all you need). Copy and paste this in there:
$DEST "cached.WAD"
$loadbmp "c:consoleconsole.BMP"
conback qpic 0 0 320 200
$loadbmp "c:consoleloading.BMP"
loading qpic 0 0 320 200
Of course, if you named your console bitmap anything other than console.bmp, you'll need to change that up there. Same thing if you're using a different directory (were you following instructions??). Now, save this document as cached.ls in the console directory with console.bmp and qlumpy.exe. Now run the DOS prompt (click start>run and type cmd), make sure you are in the console directory and type in "qlumpy.exe cached.ls". You can also type this in the run command box or you can also create a batch file to run this. Any way works fine. Whatever floats your boat. So now, the result should be a magic cached.wad file in your directory. So copy that file into the Aliendance (or other MOD) root folder. You're all done with this now. You can go ahead and delete that console directory when you're sure everything is working okay with the cached file.
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at first i couldn't get mine to compile because my DOS prompt was directed at 'my documents'. so if the DOS promt has anything other than [ C:/ ] just move youe project to the destination listed and it works, or somehow change the directory. Im not DOS savvy.
IF for some random weird reason things aren't working, pass me the images and I'll make your cached.wad for you.