Garden Wall Graffiti

Hi My neighbour recently built a lovely wall between our back gardens and I painted it white but it is the most boring wall in Dublin. I'd love if I could get somebody to graffiti it for me - I'm looking for something urban but not too busy, as I still want the garden to feel relaxing. I'm thinking of something like random overlapping disks and circles in various colours, nothing too geometrical but not balloons either (don't want anything too kiddie). Attached are pics of the wall, and I'm afraid my budget is pretty small (max EUR500), so I think it will have to be something pretty simple. Thanks.