A some of you might have seen in the http://www.gamesas.com/topic/1411547-arena-questions/, I'm working on a little modding tool for TES Arena.
This is now my official thread about that tool. I will post new versions here, do a little changelog and give explain how to use it. You can also ask me to add features.

Changelog:
Version 0.1:
(First release)
-Can edit INF files and view SET files

Version 0.2:
-Roughly parses MIF files
-"links" the INFO entries of MIF files to INF files

Version 0.3:
-Fixed a bug that did not change the output-size of INF files.

Version 0.4:
-Fixed a bug where changing an INF file after opening a SET file without reopening the INF file would not be recognized by the program.
-Added some version info stuff to the exe

Version 0.5:
-Added the option to import/overwrite SET files
-Files of size 0 will now be deleted on Save/Rebuild

Version 0.6:
-INF files of size 0 will no longer be deleted (because you can't import any, yet), when clicking Save/Rebuild
-The palette is now inside the program. Arena.pal is no longer needed.

Version 0.7:
-Fixed a heavy bug that deleted all INF files on saving. Luckily nobody downloaded the buggy version.

Version 0.8:
-Added support of 1-entry-SET-like IMG files.


NOTE: The program only supports 24-bit BMPs, NOT 32-bit! Importing a 32-bit file will add/replace it and set it's size to 0! (=> will delete it on save afterwards)

Version 0.8 download:
http://www64.zippyshare.com/v/38747525/file.html

I admit I don't know much about modding, but I love these early games and am very excited at the prospect of improving them!