As a longarm quilter, I PREFER it when my customer gives me some ideas of not only what she LIKES for quilting designs, but also what she DOESN'T like. It's the best way for me to be sure that she will like the final product. I can be the BEST 'feather quilter' (or whatever) in the world, but if you personally don't like feathers, you are not going to be happy.
I personally do not agree with the quilters who have the attitude of "they're hiring me because I'm the expert, I'm going to put what I want on this quilt, I don't need/want their input". I consider myself and the client to be partners, and even if I think the quilt would look best with teeny-tiny dense quilting, if the custom prefers looser quilting, then that is what I'll give them.
So don't be afraid to share your thoughts on how you would like it quilted. If the quilter seems offended or says she's going to just do it her way anyhow, I'd look for a new quilter.
Andi