Mine go on the lower right corner, with my name, city, State and date on the back. I always write a book with my quilts that I give as gifts so the recipient knows (years down the road) what was going on, what the headlines were, what the Twins or Vikings were doing and sayings, adages, little stories and jokes. I tried to put a little of each on each page I did. Each page was a block. So if I had 35 blocks, I would tell about it, what was in it, what it meant, what the name of the block was, etc. It is appreciated, it is provenance and it is a nice way to end a day of quilting, while it is still fresh in your mind.
I just had some bad news (not really bad, but not exactly planned. I made a little sampler quilt for our son's friend who was going to have a baby (he and his wife). The center block was called Poinsettia and it was because the baby was going to be born in December. She was born last week - with a heart problem and with Down Syndrome. I don't know if I should give it to them or if I should make a new one with bright colors or what I should do! I wrote a book for that too and right now I don't think I could give it. I wrote of all the things the baby could do with (at this point I didn't know the sex of the child - their choice) her parents, and I just don't know if it would fit in.
I keep thinking to myself - a baby, regardless, just wants warmth and a Poinsettia block in the center doesn't mean anything. I put the signature on the bottom right corner.
When I did the embroidered quilt, the "signature block" would always be bottom right, with something embroidered on it and my name, city and state and date on it.
I think where you feel the most comfortable putting it is the right place. Edie