I'm no artist myself, but I recently came across something I thought could be made into a good wallpaper. It's a block of text which is going to be put at the Waste Isolation Pilot Plant, a nuclear waste disposal facility, to warn away future generations in case the information of it's existence is lost to humanity. (the waste is dangerous for 10,000 years, after all)

I was thinking it would look good center aligned with a desolate or depressing landscape in the background. Here's the message:

This place is a message… and part of a system of messages… pay attention to it!

Sending this message was important to us. We considered ourselves to be a powerful culture.

This place is not a place of honor…no highly esteemed deed is commemorated here… nothing valued is here.

What is here is dangerous and repulsive to us. This message is a warning about danger.

The danger is in a particular location… it increases toward a center… the center of danger is here… of a particular size and shape, and below us.

The danger is still present, in your time, as it was in ours.

The danger is to the body, and it can kill.

The form of the danger is an emanation of energy.

The danger is unleashed only if you substantially disturb this place physically. This place is best shunned and left uninhabited.