I want to point out that it isn't only art and copy rights that can lead to a lawsuit for indie developers.
Every thing you use that was made by someone else is a potential lawsuit, from game engines to file formats and third party plugins. As a indie you will be using things made by others, making every thing yourself is near impossible and at best will waste the time you could be spending on the game.
The best you can do is to follow the law and when in doubt, you can bet you will be sued.
My question is: is there a realistic chance for a small indie to get sued over something?
Small indies often have to deal with legal matters, however you will often receive a warning allowing you to take action or prepare yourself.
Does that chance increase a lot if you ask money for the game?
I think Minecraft is a good subject to study, after it became popular people attempted to sue the developer for all kinds of reasons.