Some files (such as the ones in the folder 'onmap') end in extensions of .tex and .tpl. My guess is that .tex stands for "texture" and .tpl stands for "texture palette". That being said .tpl files seem to be decompressed palette files and .tex files seem to be compressed with LZ77-11 (I did not try myself). I don't know much of anything about textures but google and sites like http://www.romhacking.net and http://www.gbatemp.net will likeley help you find out what you need to know.