I think it's important to increase aesthetic properties for donators to make the donator group seem slightly more special. These could include the following.
- New emoticons for donators: Have some special emoticons only donators can use, don't REMOVE access to any current emoticons but simply add some new ones that donators can use, these new emoticons can be used to show off and often will have people going "How did you post that emoticon?" "OH! You can post it if you donate" "OH COOL!" (they don't have to be custom emoticons, they can be ones you can download.)
- More transparency in the donation process. It's important to know where donation money is going, whether we are on the right track or not. It can be very disappointing and self-defeating if you donate some money and you don't actually know what the money has done to improve the site. Some more transparency and publicly available information on the donation process could be good, have graphs of what we're expecting and what we're getting, say exactly why we need the donations and what service we use. This could be done on a thread in announcements.
- Have a list of our donators! A simple thing can go very far, simply have it as an option that if someone donates, they can show up in a stickied thread (in the announcement boards) that shows how much they've donated altogether. Not only would this give reputation to those who donate, but would also allow us to keep track of how much money people donated.
Those three I think are very good ideas I'd strongly recommend (the second and third option more strongly than the first), here are some other ideas that COULD be implemented if we so desired.
- Waver some of the limits for donators, allow more than 150 Kb attachment for donators, or ability to upload a higher quality profile pic. The reason we have the attachment thing in place is primarily for spammers and we know those who donate aren't spammers, so it'd be ok!
- Have donators not receive TFF ads for the period they have donation status, simple enough.
Another idea that I implemented in my clan (that actually got us a lot more money than previously) is have multiple donator levels. We had three levels, donator, donator+ and sponsor. You were given donator for paying any amount of money, a donator+ for more than $20 (altogether) and a sponsor for more than $50. Each rank of donator gave more perks. This gave our clan a whole lot more donations, enough to run our clan and enough to store some away, this is impressive considering we have permanent donator statuses (that is, if you get donator, that sticks with you forever, it's not temporary).