While I do take my 'cue' from the quilt top design I also like to improvise. I will sometimes take a copy of the whole quilt top design, put it in a plastic sleeve, and then use wipe away marker to 'try out' various designs.
If you can draw it you can quilt it. So practice drawing.
The more you look at the quilts of others and look at the various resources available: books and web sites, the more you open yourself up to doing more yourself.
ali