There are many art forms applicable to wall art, and among them, and certainly not the least, is the form of fun. Art is usually serious anyway, but the medium does determine the message. And in this case, the medium being simply a wall, less serious themes are more amenable to the message. And more fun.
Experiment. That is one way wall arts can be fun. A wall affords the possibility of simply repainting the whole thing in case things turn sour, and with a wall that is initially in poor paint condition, that is the best place to begin. Abstract wall art is often a good them to experiment with, and the thing is, if the outcome seems a bit undesirable, you can always keep adding to it, all the while maintaining the abstract motif.
Then if you finally get tired of adding and adding to your work of wall art, the solution is to simply paint over it. Then you can start over again, and maybe with another style, if you have found out that the abstract is not within your realm of skills.
And that is the beauty of art. Certainly, masterpieces have withstood the test of time and maintained themselves as masterpieces, but that is only one aspect, one characteristic of art. Art can also change, adapt, and be redone. While a work of art may have a certain appeal at the time, it is just human nature to get over things, find newer things and replace things. And that is still art.