If you need to create a map within the American FactFinder (Census) and you need to customize (change the basemap, color, etc.), after you have created the map itself using some of the following data tools:
First, create you map from the Tiger Web
You can then select your basemap
For help in using the products, see these tutorials:
Downloading data from American FactFinder to use with Tiger/Lines Shapefiles
Joining Census Data to Tiger/Line Shapefiles
Data Gems: How to map using the American FactFinder
Downloading & Mapping Census Data: Census Tutorial, Tufts University