Adding more variety to a day full of variety

Although the card selection will offer plenty of variety during the day, I've been thinking about how to keep things interesting during the day. First, we'll probably try to change the draft format with each new draft. We can start with a regular draft, but at some point I think a Backdraft (pick the worst cards possible, then pass them to someone else to build with) is something we'll have to do. One of our players will be out during the morning, but once we have all 8 available, a Two-Headed Giant draft is bound to happen as well.

I'm wondering if we should try any rounds with deck building restrictions (like playing all 5 colors) or not. I'm not completely sold on the idea yet.

I recently found a bunch of packs that I hadn't opened sitting in a box on my shelf. After going through all of the relevant stuff, I found 19 packs of Unhinged remaining. I'm thinking of giving them out as "event prizes" to the first player to accomplish a certain task during the day. (Think of it as unlocking an achievement.) Here are the ones that I've thought of so far:

• First Legendary card in play
• First creature with power 7 or more in play
• First creature with power 10 or more in play
• First creature from Homelands in play
• First spell from Fallen Empires played
• First silver bordered (Un-set) card played
• First Planeswalker in play
• First creature with 3 or more colors in play
• First creature with 5 colors in play
• First player to deal a poison counter to an opponent
• First mythic rare in play
• First player to have 3 or more different slivers in play at once
• First player to have 10 or more token creatures in play at once

That's what I've got right now. Any other ideas?