I love planning bridal showers. You can get really creative with the theme, more so than you can with the wedding.
When choosing a theme for a bridal shower think about two things:
1. What interests the bride (and groom) have. Are they book lovers, wine lovers, world travelers, chefs, etc... Their interest can help you decide on the type of party to throw and the party details.
2. What type of gifts the bride registered for as well as needs and wants. Couples who need everything for their home may benefit from an "Around the House" or "Around the Clock" shower which tells guests to bring specific items for the home. A couple who is doing a lot of home renovations may benefit from a "Home Improvement" theme where guests bring tools and other items to help their renovations along.
A shower's theme can be included on the invitation, decor, entertainment and favors. It's okay to make it as cheesy or as refined as you want as long as you keep it in the span of what the bride would like and want at her shower.
Remember that you are planning her shower and therefore you should keep all the plans tailored to what you think/know she would like. when it's your shower you can ask/tell your bridesmaids and mom what you would like.