I went to Big Day Out NZ in Jan 2011 and required a smallish compact bag that could be carried across the shoulder and remain unobtrusive whilst being light and comfortable.
So I crocheted two rounds about the size of side plates, cut two matching pieces of fabric and sewed to the inner side of each round.
Then knitted a strap that was long enough to wear in the fashion mentioned above. I stitched the ends of the strap together and made sure the join was at the bottom of the bag then stitched the rounds to the strap as shown in the diagram below matching each of the points but leaving enough of a gap for a zip at the top. The last step was to insert the zip. between the blue and green crosses (refer to diagram)
I hand painted the skull with textile paint on white roman blind material and fixed it with an iron. I then blanket stitched it onto the bag.
The day was great, the bag performed well.
The only thing I would do differently would be make the strap a little shorter at the beginning, because with weight of the bag and contents the strap is going to stretch over time….. Mine has stretched so long in the strap that I tie the top into a bow over the shoulder to keep it from hanging around my knees.