Somebody please say this isn't true..
EDIT: I've already converted everything over to PNGs with XNView.. but I just like TGAs for some reason... any reason for their departure?
3.1.2 hasn't changed support for any file formats.
There was a change in supported file formats between 2.72 and 3.0, at which point PCX and TGA were lost, and JPG and TIF were added instead. This was as a result of AGS switching from custom file import code to using the standard Windows file import routines.
I'm sure there's some converter that will also quarantee lossless quality.
He already mentioned using XNView to change the image to PNGs. No quality is supposed to be lost this way.