There is no real hard or fast rules when it comes to choosing wall art to hang together. Except to say go with what you love. Often I have customers that say they love 2 completely different prints and worry they don't go together. I think it doesn't matter. An eclectic mix of wall art and décor becomes a cohesive look in itself.
But if you do want to find wall art that naturally hangs well together, here are my tips.
1. Look for designs by the same artist. Each artist has their own signature style and look, so often their designs will have a coordinated look.
2. Look for designs with a similar colour palette. Even when art is by different artists, if they share a similar colour palette or even just one dominant like colour. They will hang well together.
3. Look for designs that have a similar theme. Again these designs don't have to have the same look or feel. It is the subject matter that ties them together.
4. Typography designs are a great way to addpersonality to a room but are also easy to pair with any picture design.