I would like to know if is it possible to use a theme for one application and use another for the remaining of the system? I use OpenBox and I change themes with Lxappearance...
Use Lxappearance to set the theme you want for the whole system and then to launch a program with a different theme you can do:
bash -c 'GTK2_RC_FILES=/path/to/second/gtkrc programname'
Uhh, thanks mauryck for the question and anonymous_user for the answer! I use a very slow gtk theme, and one program suffer from it, but this theme is so beautiful so I dont like to change. Never though about this solution, use a different theme only for this program!
Sometimes the solution is so simple...