
We are working on PS game translation using GIMP. Some of these TIMs use the alpha channel and some are already indexed!
My procedure is :
1) Open a tim--->extract bmp with TimViewer
2) Modify the bmp
3) Transform on indexed mode (16 palette)
4) Save the bmp and convert on .TIM
Everything looks OK...even the size of the .TIM
But, we have a couple of problem about this format...
1) It's possibile to mantain the original .TIM's CLUT?
Because, after i working with GIMP it modifies the CLUT using this kind of colorset. Check it out :

original TIM

modified TIM
The other problem is...
2) How a font looks good on indexed mode?
Some .TIM, can't be edited with a font because sucks so badly. They are sgarnished and pixeled.
Here's an example :
original
modified
Thanks a lot!