As we all know, voting helps to bring the server higher on server lists and thus gives better chance of attracting new players. My suggestion is to encourage widespread voting by awarding the top voter of each month with a USD $5 or USD $10 voucher to be spent in the server donation store. With this monetary reward, the top voter can buy a rank if they are not a donor. These vouchers can be accumulated by being the monthly top voter multiple times, so players with higher donor ranks can spend the accumulated vouchers on a rank upgrade.
In addition, top voters can also be given a [Top Voter] tag on all subservers to recognise them for their dedication in voting daily. The only issue I can think of is that the top voter position may end in a tie, which makes awarding the prize more tricky.
Feedback is appreciated. Thanks.