Donation Incentive Program (DIP for short lol)

So, im considering starting an incentive program for people who donate, and im open to ideas at this time. What i would like to see, ultimately, is 3 separate incentives. 1 for level 0-14, one for 15-27, and one for 28-cap (38). what sort of prizes should i have for that? The most useful common item i can think if is to maybe give half their donations back. The company still benefits from their donations, that just means ill have to keep a few million lying around, and that will take away from the company in that the time that it takes me to save that amount is time im not donating. Prizes will be awarded every time the company levels, or on a weekly or semi weekly basis. Ofc, all these are just ideas at this point so everyone let me know what you think!

the incentive for me is the next set of stats that i get!!!