Cake decal
So I wonder why Valve put the textures in and not the vmt's? I'm only guessing here... but... test chamber signs?
Also the newest version of PakRat (which isn't very new tbh) can put custom material into your bsp. I highly recommend you to pack the custom material into the .bsp if you are only going to use a tiny amount of custom content, however if you are going to make a whole load of custom content (or have more than one map after the other), use a vpk.
Thanks for the help everyone. I'll play around with this on my next free day. 
As a manufacturer I will offer a standard guarantee that the product is good for use, however, it will be your customer service that decides whether customers are correct/incorrect if any problems arise. If my work is below standard (which it wont be because I dont need the hassle!) I will happily replace anything that is actually my fault e.g. a bad cutline or a printing error which might not be picked up straight away. A printing error is defined as; colour banding, ink spots or a head strike/scratch on the wall decals. 
Spambot, banned.
If not a spambot banned anyway, that is really shameless advertising.
Now with 100% more inline comments!