Is there a big difference in photos taken with the Canon 100mm macro lens, with the 100D body vs. the 7D? I have a Canon 100D and it looks like photos taken with the 100D are terrible, nothing nice and beautiful!
Doing a quick search of Flickr using Pixel Peeper returns the following results for
100D with 100mm f/2.8 Macro - http://www.flickr.com/photos/21046994@N08/9256855808
7D with 100mm f/2.8 Macro - http://www.flickr.com/photos/32339529@N04/5351386823
Both cameras are able to take fine photos using the Macro lens. The problem exists between camera and ground. Try working with better lighting and a good tripod. This should help your macro photos come out much better. You may also have to use a smaller aperture to get a deep enough depth of field for the kind of shots you want, which may require longer exposures, depending on what you are shooting.