Choosing the theme blueart_no_1 makes IceWM hang (though the active XTerm window is still responsible). After restarting (Ctrl-Alt_Backspace) IceWM runs but it has two icewm-sessions taking all the CPU resources.
Thw solution is to change the theme to a correct one manually (~/.icewm/theme) and restart IceWM. If you still want to use blueart, you need to comment DesktopBackgroundImage="background.xpm" in /usr/lib/X11/icewm/themes/blue_art_no1/default.theme as it's not an xpm-file, actually. You also need to comment everything concerning taskbar (solution found by agent_007).

Steps to Reproduce:
1. Choose the theme blueart_no_1.
2. Restart IceWM.
3.
Actual Results:  
IceWM hangs.

Expected Results:  
IceWM changes the theme properly.