In my opinion donations spoil the game for players who can't pay. So here is an interesting and fun way to reward your players with custom items (ones you've made of course). The best part is that players will enjoy it and feel as though they have accomplished something on your server. These custom items will have to be earned (some of them through pure luck, others through hard work) so not everybody will have them, thus adding to their specialness.
• If your server name can be made into an acronym (let's say your server name is Really Good Server) then make items that are named with each letter of the acronym (Have an item named "R" another one named "G" and another one named "S") and then hide them throughout the server, whether it be a drop off of a random mob/boss or loot in a chest, or maybe even randomly choose a player and mail them a piece. Once a player collects all the pieces they can use it as currency to buy one of your custom items
• If you hold events on your server then you can make a special trinket or ring for event participation (The yellow words that are found on an item, called a description, should say something like "I won/participated in X amount of events!" this way other players know how it is gained and it will keep the "OMG WHERE DID U GET THIS?!! down to a minimum).
• Have guild wars, whichever guild has the most members by the end of the week will get a reward (this should apply to guild masters only and it is important that only the guild masters know about it otherwise you will bring havok to the server, and it might force everyone to join a single guild, thinking that they all will get rewarded).
• If your website has forums then you can use this for more than just support. Hold a contest to create bosses or items, whoever has the most or best items/NPC's will get a custom item (as well as see their creation implemented into your server). The forums will serve as a place for them to share their creation with you as well as upload it to you.
• Want to improve your server? Hold a contest to see who can find the most bugs. Every bug counts as 1 point. If the person also has a solution to the bug then that counts as 2 points, so a person who finds 4 bugs but no solutions will not win against a person with only 3 bugs but a solution to two.
That's all I have for now, if I come up with anymore I'll add them.
Credits: Myself, if these have been seen before it is by complete coincidence that I happened to think of them as well.
Hope you enjoyed!