Thanks guys, your replies finally sorted something that kept me busy for quite a long time lol. And as often, it’s something very simple - don’t use RLE compression…
@Gisteron: I’m guessing that your graphical program took the original image settings when you imported it, and saved it the same way.
@Chips: thanks m8, that topic was very helpful as well in regards to the fact that not even all images are really needed for the game.
Cheers guys.