Here you go.
Only supports 2 pixel types for the JIMG because the sample files you gave only has those two.
jTexTool
As for those JCMP files, drag them onto the window in jTexTool and it will decompress them for you.
If you find any JTex files that don't work, upload them.
Edit:
Node: You must open the .jtex you're editing before you create the new jtex files because there's some header stuff I didn't bother to figure out and it will be copied.
Only supports 2 pixel types for the JIMG because the sample files you gave only has those two.
jTexTool
As for those JCMP files, drag them onto the window in jTexTool and it will decompress them for you.
If you find any JTex files that don't work, upload them.
Edit:
Node: You must open the .jtex you're editing before you create the new jtex files because there's some header stuff I didn't bother to figure out and it will be copied.