It's common for wad files to be all caps. The doom-shareware rpm from rpmfusion.com installs DOOM1.WAD for example, so it would be nice to just give -iwaddir ... -doom1 as arguments without needing to also give -iwad DOOM1.WAD

ln -sf DOOM.WAD doom.wad

This belongs more to FR requests I guess. I think it's bad to push the burden of doing this on the player (symbolic link in the post above). I was stumped by half an hour and there was no suggestion that it was caused by upper/lower case. "No IWAD found" message is not informative enough. It would be much better if it said, for example, "heretic.wad not found". Related issue: -iwaddir option doesn't seem to do anything. I have a few source ports and would like to share .WAD's between them. I tried both DOOM2.WAD and doom2.wad, and it still wouldn't find the wad. (This post is still valid in 1.31)

-iwaddir should only specify the route (i.e. no DOOM2.WAD, only C:\Doom2).