Well there are plenty of places. But you need to understand that it's not that easy. Do you have permission from the event organizers to sell images of the event? Were you shooting for a press agency or magazine? permission of the band and a model release? If no, then no one will touch the images, sorry. Copyright and permission are vital to stock houses and agencies to keep law suits to a minimum. And for you, you can not just take images from bands and events and sell them. Even if you think it was on public land and free to enter, there will be rights issues. If you paid for a ticket, you are almost guaranteed to run into issues. And if there is no understanding with the band, you will definitely not be able to sell them. If they have a recording contract, you'll get a letter from a lawyer for sure. Making money with images of other people isn't as easy as it sounds. Especially when they rely on imagery to shape their brand, which they then rely on to make money.
Also, the term 'royalties' isn't really one that applies to images very often. Images, or more correctly, usage rights are usually sold for a flat fee. A fee that is largely based on how it will be used. Which complicates things even more.
