Boosting wondrous magic items

[Gwyllgi]

Are there any ways other than meta magic to make wondrous magic items stronger or more effective. I've got a major Iceheart off of a enemy and made a ring of icy soul. The reason for this is that my DM hase allowed me to substitute my Major Iceheart when casting the spell Heart of Stone. I cast it extended and am doing pretty well whenever we aren't in a cold climate where everything has a resistance to me. So I wanted to know if anyone knew of any ways to boost wondrous magic items to make them stronger.

[Jowgen]

The Enhance Item feat can boost the Save DC of the Iceheart's spell depending on who did the enhancing, while Dark Speech and Words of creation and provide a free +1 caster level boost for the item.

[Thurbane]

Karsus (vestige) ToM p.37: Heavy Magic. The save DC for each effect of every magic item you use increases by 2.

Will require 3 levels of Binder, or 1 with the Improved Binding feat. The Practiced Binder feat also works, but has a two req feat tax.

[Troacctid]

Inspired Master feat from Dragon Magazine #339 gives a flat +1 bonus to caster level when using any magic item.