Spent some time customising my regular cars and ended up with some uploaded artwork which is free to anyone who wants to use it.
I know some on here have done some awesome stickers to share and thought we could list them all in one place.

PH username	Gamertag	Objects	Cost
DocJock	johnnyy13	Nurburgring 'N' sticker, JustGoFaster 'donkey' sticker	both free to share
The_Jackal	TheJackal GN	PH Logo	Free
Ikemi	ikemi007	M25Ring Logo	2,000cr :P
S3_Graham	GSI 2000	PH Logo, Ring sticker, Nismo Logo, Trackday stickers x2, dunlop logo	Free