I would like to do one of those open box cakes where the lid is lifted and flowers are coming out, can anyone tell me how to support the lid open? also I was thinking about using a 10 inch heart shaped pan, will this give me the same amount of servings as the round?

A 10" round pan will give you 28 servings. A 10" heart-shaped pan will give you 24 servings. For help calculating servings see this link - it's a wonderful tool from metria, a CC member:
http://shinymetalobjects.net/cake/calculator/cake_calculator.cgi
You can prop up the box lid with a dowel which you can hide with the flowers you'll put around it. Just make sure the dowel goes all the way to the base of the cake. HTH!

Would love to do one of these also. In this scenario, is the lid actual cake or is it a board covered in fondant? Have heard of both but wanting to know if it is actual cake, does the dowel thing still work. thanks!!

Yes, I think it would still work, because you would have to put it on a solid base, and the dowel would be holding that up. People have also made the lid out of gumpaste, with sides like a real boxtop. You'd probably have to have a cake base under that, too, to keep it from folding.

I've done a couple of gift cakest are in my pics and the lids on both are gumpaste. I just use the pan that I'm baking the cakes in, turn it upside and drape the gumpaste over the pan. I trim it, cut at the corners and then "glue" the corners back together with a little bit of water and let it dry for about a week. Then turn it upside down, and let it dry on it's top, so the inside is up (is this making any sense?! lol), and let the inside of the lid dry completely hard

Makes great sense, yummy_in_my_tummy! When you flip it over, you remove the pan so the inside can dry, right? I still think I'd use a cake base because, where I live, gumpaste never dries completely (they keep telling me humidity is great for the skin, but it's the pits for cake decorating!).

The covers of these 'boxes' are made of a sugar cookie covered by a thin layer of cake. The whole is then covered in fondant:

http://lamaisondesgateaux.blogspot.com/2010/12/boites-en-forme-de-coeur.html

The cover for this box is made of foam core covered in fondant. If I was going to do it again, I'd try the cookie simply because I really prefer as much of my work to be edible as possible:

http://lamaisondesgateaux.blogspot.com/2010/12/un-gateau-de-chocolat-couvert-en.html

Tres beaux, cakeyouverymuch! Love your blog! I just marked it for my favorites.