All of the above would be good ideas, and in addition, you might be able to get people to pay for a "premium" membership. This could include sections of the forums which are off limits to "free" members, or giving paid members access to apps which free accounts can't use.
Another option would be giving people the chance to offer services in exchange for premium membership. An example would be someone makes a scroll, or perhaps some piece of armour/garb, which they give to the site, and then the site could sell that item. The maker of the piece would gain premium membership for a number of months based on the value of the item (either sold through the site itself, ebay, or some other online merchant), while the site keeps the proceeds from the sale.