I have attached two patches, one for bsetbg making the use of display command for setting the background a bit more flexible about your desktop size using the info from xdpyinfo, and the other one for commonbox-imagebgmenugen adding a pipe to sort the list of images found in /usr/commonbox/backgrounds so that they appear in alphabetical order in the menu :-) If anyone else is interested I could create a patch for commonbox-imagebgmenugen to not only change the background for the current session but to keep the setting of the background to your ~/.fluxbox/init file automagically. It seems quite easy but I don't know if people prefer the way it works now so I'm waiting for some opinions first.
Created attachment 14971 [details, diff] bsetbg.patch
Created attachment 14972 [details, diff] commonbox-imagebgmenugen.patch
I forgot to say that I changed the command that was used in commonbox-imagebgmenugen to load the backgrounds from xv to bsetbg as xv isn't installed by default (at least not in my system) and bsetbg seems to do its job pretty well working with imagemagik's display program (especially with my patch).
*** Bug 25766 has been marked as a duplicate of this bug. ***
Another addition to the changes that should be made is the a little change to the order where the apps appear in img_apps. Esetroot should be put in the front as it allows the use of transparencies in fluxbox 0.9.x series. A new version of fbsetbg is also available with some new features. Check http://fluxbox.sf.net for more info. Maybe fbsetbg could be used instead of bsetbg in the commonbox-utils package?
commonbox-utils-0.5 totally replaces bsetbg/bsetroot,xv with fbsetbg and feh. This should solve the complaints seen here with the previous scripts.