I can suggest two online tools that I think will really help. One is a comprehensive slide show that provides multiple ideas for various types of windows. Check out The Ultimate Guide to Window Treatments.
Narrow your search to the type of window you’ll be treating. Will you be working with double-hung windows, casements, banks of windows, windows in pairs, single windows, transom-topped windows, or patio doors? Start with one type and use the slide show to see what’s available.
Once you have a general idea of the options, it’s fun to try out different styles and colors for the windows you’re trying to treat. The Try-a-Window Treatment tool gives you a way to do that before you go shopping.