Yup there sure is. Though I had enough items to spend the entire budget, all gametypes, and plenty of weapons.
I believe the custom content has been bumped up to one thousand, but don't quote me, please. In addition to the object limit number, there is a categorical limit for certain items, IE you can only place up to one hundred building blocks. I say only, of course, when it is still a huge leap ahead of Halo 3.