I see that in at least some cases, .tga format is preferred for 2D images. I would think that the dev work just hasn't been done yet to accommodate other file types, if I didn't see that the API sometimes requires that filename be specified without extension, and ".tga" is added. Why the Microsoft-like infatuation with a format that takes up 12 times the diskspace as PNG to accomplish the same goal at runtime? PNG has worked perfectly for everything I've tried to do texture-wise, and the modeling tools seems satisfied with it. Maybe there's some limitation with PNGs that I haven't run into yet?
jME is fine with any image format AWT can read. You have probably looked at one of the third party MD5 importers, which uses .tga because that's what MD5 models usually ship with.
I don't see any cases where tga is appended? I think you might be using the ResourceLocator classes which try using several formats before giving up on finding the texture. jME supports by default all of Java's formats with special loaders for DDS and TGA.
Thanks for clearing that up! Glad to hear it.
Must have been third party importer APIs. My head is filled with tons of JME-related docs from the past week. Sorry.
The AWT PNG loader is terribly slow. The jME TGA loader is fine. You should consider that too, if you load lots of textures.
You should convert your textures to .dds files if you want to be able to load them fast. That way you get rid of the costly load time mipmp generation, which is by far the heaviest part of texture loading.