You should be able to do that by setting the TV as a second display. You could mirror but then what is on your Mac will be on the TV so if you are using your Mac to DJ then you won't see your audio software. If you use it as a second display and know your playlist order in advance, you could put together a presentation of the covert and just advance it with each new song. If you don't, you'll need a way to quickly find and display each cover while you are playing the song.
If you have playlists built in advance you could use software such as PhotoMagico to create a slideshow with cover art synched to music. This would allow fades and other effects as well but would not be a live performance.
If your dj software will display cover art and has a presentation mode you could simply use that.
To ensure sound does not go to the TV verify your audio settings are not set to TV.
Most importantly, test your set up in advance so you can be sur it works and aren't trying to fix a problem 2 minutes before you start...