Dungeon exclusive items could be some of the cheaper prizes maybe.
Some ideas perhaps? You get 2 BP/VP (VP = Voting Points) per vote.
2 BP: 3 Iron Ingot
5 BP: 2 Gold Ingot
10 BP: 1 Diamond
25 BP: Your Playerhead
50 BP: Nether Star
75 BP: Repair/ Heal Sign
100 BP: ? Bedrock
This system can get a new player started when they vote, and will satisfy older players with the Nether Star. 
But then again, these are just ideas. So don't take them to heart if you don't like some of them.
if these two could be combined and balanced, I'd be interested to see what y'all come up with.
Try to consider how long it would take per item.
We currently have only 2 voting sites (subject to change)
And you can only vote 2 times per day.
With tymac's approach, it would take 50 days, or a month and a half, to get bedrock. Imagine how long it would take to get a stack of it, a small room made of it, or just a cool decoration with it.
Other options: apples/bones for people who want to summon mcmmo pets quickly.
If you do propose an addition/edit to the list of items, try to include the previous suggestions.
EX:
Mio says "I think apples should be 5BP (VP?
) and bones should be 8BP"
I would say "How about apples are 5BP and bones are 10BP"
Tene would say "apples should be 20BP and bones should be 200BP, and what about adding diamond blocks for 20000BP"
