I downloaded a batman 2pack skin from alex's site and I opened it in gimp and the tga was empty or invisible, the extras the portrait the TM stuff, what does that mean?
Assuming you mean the pack by C6, I opened them in my favorite editor, irfanview, and they looked fine there.
I have noticed that some skins don't show up in nifskope but are fine in game. If i open them in irfanview and then save them with it, then they appear in nifskope.
what editor do you use
irfanview, as I said above
is there a way to fix my issue with gimp and the skins not being visible, is there an alpha channel thing?
No idea. I don't have gimp so I have no experience with it. I don't think its an alpha channel since irfanview doesn't deal with it that much.
what can you tell me about RLA compression
Not a thing - graphics/ textures are not my thing - I just know the bare basics.
https://www.irfanview.com/ -irfanview is a free image viewer software, tl;dr everything RD said is true: nifskope doesn't like certain tga compression software, though it should load fine in CTool and ingame. Simply open the offending tga/dds in Irfanview, CTRL-S to save, save as tga/dds, and you should be fine.
The only thing you should have to fuss with settings is if the file has an alpha channel. If you need it just for refence on a skope and don't want to mess with it, just duplicate the folder and make a version without the alpha. Again, the file works fine in-game, it just doesn't show up in nifskope.
Thanks Tomato