Graffiti-proof Wall?

This up here is my first ever tablet drawing.

My dad got me a Bamboo Pen last night so here is what I end up with the next day. There is no direct concept, just a random idea upon random idea. I did it straight on the laptop because I was very excited to try this technology out. I'm starting to develop more interest in digital art, looking forward to doing more.

Equipment Used:

• Bamboo Pen 
• Adobe Photoshop 7.0 (old school and can still kick ass)
• My own sketch of clouds on paper, scanned