The program could randomly select from a list or a directory which screen to use each time a background is displayed.
You wanted it? Here it is! http://rapidshare.com/files/78166410/COHOKUM.RAR.html
There is an additional parameter in the eech.ini called "themes" in "[Graphics and Textures]" section. (NOTE: You must run cohokum.exe once to update it first).
If you set it to something like this:
themes=one,two,three #Note - no spaces, just commas
On startup EE will choose something randomly (for example, "two") and then...
If it is required to open
first of all it will try to open
and only when this file is missing the original file will be used.
So, you need to create additional directories, put some new files there and write these directories' names into eech.ini.
If you have more wishes about such functionality - fill free to ask.