Well, there is a solution. If you know where to get Launcher Pro, ADW Launcher and Go launcher EX, half your problem is solved. Go ahead and install all three of them if you want to have all your options of a cool UI open in front of you. Once you have these three launchers on your phone, you can go and download N3XGen Theme Manager
N3XGen Theme Manager takes the chaos of themes available in Android Market and organizes them in a way it is to easy to discover themes that suits your taste. It allows you to search themes. It categorizes themes into free and paid. It syncs your Application Data from the Android Market so that you know which theme you already have and which you do not. The App is in beta. There are more features to come.
Here is a video of N3XGen Theme Manager: