If you need a tattoo covering up, there are obviously some limitations when looking for a suitable design. When considering a cover up piece do some research into what type of design will work best. Get a few ideas together of what you would like but be prepared to be flexible!
Generally a cover up design will need to be a lot bigger than the existing tattoo. It will also need to be fairly dark in places to achieve the cover up (not necessarily black though). Sometimes a studio will recommend that you have some laser removal to see if the intended cover up can be lightened a little. This can often give you many more options with regards to your new design.