Each style can have its own "graphic sets", what you want to do is copy all data from the "images/general/default" to "images/general/custom"; and set the "General Images" dropdown in your style to "custom"; now any "global" changes from an upgrade go in the default folder, and any customizations are retained in your "custom" folder.

I am a Web Development Contractor, I do not work for UBBCentral. I have provided free User to User Support since the beginning of these support forums.
Do you need Forum Install or Upgrade Services?
Forums: A Gardeners Forum
UBB.threads: UBBWiki, UBB Styles, UBB.Sitemaps
Longtime Supporter & Resident Post-A-Holic
VNC Web Services: Code Modifications, Upgrades, Styling, Coding Services, Disaster Recovery, and more!