Next in the process of learning beginner guitar chords are adding some simple minor 7th chords. Some of these are very easy to learn to play (e.g. Am7 and Em7), yet they add a great dimension to a song or chord progression.
They tend to be a little jazzier and somewhat "softer" sounding than the dominant 7th chords. Examples of popular songs using minor sevenths are "Light My Fire" by the Doors and just about anything by Neil Young!
The chart below shows several fairly easy-to-play minor 7ths. Try the Em7 and Am7 first as these are easier to finger properly ,and then add the other two to your repetoire of chords for beginners.