For now, it starts to look like something already, but, there are a few things missing.
The archs and the text are looking waaay too basic, so lets make them look more interesting!
You can do this by grabbing your favourite brushes (grunge works well, I used some paint brushes I found on DeviantArt) and start brushing on a new layer, using the backroung color.
This will prevent you screwing the entire image, and having to start again, because the undo function didn’t cover it.
I would recommend doing this layer-per layer, starting with the text, just get wild, but dont overdo it!
Then make a new layer again clean the parts of the image you do not want to be covered yet, and repeat.
If this is just a bit too quick for you, just look at my progress, all the “decoration” is done on seperate layers.