My Fiance and I are in the same boat. We absolutely adore Disney. Our invitations have Mickey and Minnie on them... got the cake topper... got the bride/groom ears for the rehearsal... and I'm going to walk down the aisle to "A Dream is a Wish Your Heart Makes."
For our decorations, we've taken on many things... to our disappointment, there just wasn't very much online for a mickey/minnie themed wedding.
Our centerpieces are 10" glass pyramid candle holders. We etched Mickey heads around them, and will be placing 6" red pillar candles inside (our colors are red and white). The candle holders will sit on large mirrors which will have scattered Mickey heads that we've punched (with a 1 1/2 in Mickey Head paper punch) in red vellum and in wallet-sized pictures of us together or when we were little. Hopefully, the pictures will provide some extra entertainment/conversation at the tables! You can order photo confetti online... but our venue didn't allow it, which is why we're doing extra-large paper punches.
As our ceremony is outside and my dress has quite a train on it, I've decided that I MUST have an aisle runner. Unfortunately, I couldn't find ANY aisle runners that were not transparent lacy material (I can't see that being outside). Anyway... some crazy part of me decided to make a runner myself... so I've been working with 11 yds of white canvas! I'm in the process of painting it now. When I'll walk down the aisle

(or when anyone is facing the "altar" outside), you can read "Once upon a time"... and when we leave, you can read "And they lived happily ever after..." It's taking longer than I expected, but I'm quite pleased!
I hope this helps! If you have any questions about these ideas or want pictures, I'd be happy to take pictures for you!