I'm not sure why you were having problems with sidebox or centerbox titles, but I have tested the complete mod in Firefox, IE8 and IE "compatibility" and found it to work correctly.

Images for Titles v2.0 is now available in Free Addons.

Moved image replacement to function for more flexible use,
added easy image filetype define,
added image replacement for subcat names in category listing.

Base files up to date as of v1.3.9f.