Somebody in a forum I was on mentioned that it would be cool if you could spraypaint a custom picture on the walls like in the Counter-strike games. Well, I thought it would be an interesting brain teaser to try to make it, so I spent yesterday fiddling with it. Here it is.

Link: http://skyrim.nexusmods.com/mods/27683

Description:

Graffiti: Tag Anything!

Installation: Simply extract all contents into your Data folder. Allow folders to merge
as the computer requests.

What this mod does is allow you to "spraypaint" a given picture on a wall (but not floors
or ceilings unfortunately).

The default picture is of the dragonborn symbol, but you can change it to whatever you like.

Finding the Spell:
When facing the arcane enchanter in Farengar's (the court wizard of Whiterun in Dragonsreach)
office there are doors to your left and right. Go through the one to your left and turn.
There is a small table there with the tome.

Using the spell:
It is basically point and click. It doesn't work on ceilings and floors, but works on all walls.
However, it is best to find a large flat wall, as if the projectile hits an oddly angled
surface, the results are...less than optimal.

Only one tag can be placed at any time. This is for two reasons. Firstly, it prevents save bloat
and secondly you can't actually "spawn" decals, you can only move them around. So, for now
there is only one at a time. I may fix this, depends on if it is possible to fix or not.

Changing the picture:
In your Skyrim/Data/textures/Graffiti folder there are two files, myGraffiti.dds, and myGraffiti_n.dds
With Gimp and the .dds extender you can take any picture you want, export it as a .dds
named myGraffiti.dds and move the picture into the aforementioned folder and replace the
existing file. Voila! For best results make the picture 512x512 pixels and also make a normal map.

Making a normal map:
http://custommapmakers.net/index.php?option=com_kunena&func=view&catid=18&id=1715&Itemid=54

The instuctions look complicated, but its really very easy.