Custom Icons for Pwned iPhone\Winterboard.

I’m not going to lie, I am very, very tired and don’t feel like sorting through all the junk on the Pwn site so I’m just asking you guys here;
Is there a way I can upload my own custom App Icons into a Theme I download from Cidia for Winterboard?
I have a really cool Theme I downloaded and I want to create some icons to go with that theme for Apps that don’t already have a custom icon.