Oh, I love it! Your colours are fabulous. Maybe if you feel like quilting the centre, this gives you more room to "play" with. But no matter what you decide, it will be gorgeous.
Maureen

Perhaps you arent' happy with the center because it is so dark. It may look like a big hole in your lovely plates from a distance. The size looks good. Maybe you should try a completely different fabric that coordinates with the rest. Or maybe just use a lighter one of the ones you've used for petals. The dark purple center may look just perfect if you put a dark purple sashing between the blocks. What is your background fabric?

Another idea is to applique something (lighter) in the middle of the dark purple center.

Very pretty.

I think that is a great idea.

This was my thought also. One of the problems with quilting we all face is the numerous choices; yet that is part of the fun also.

I love the Dresden block and the colors are very pretty. I would not have thought the center was too large if you had not mentioned it. I think its a personal preference. If you feel unsure, try a few different sizes until you find what you like. You can't lose---its will be a beautiful block.