I had a sneeking suspicion this topic would take off.....
I've thought of couple more,
here's a couple for someone with bad teeth.........
"you've got a smile like a row of condemned sh*t houses"
or
"you've got a smile like a smashed stubby"
someone with not so good looks,
"you've got a face like a dropped pie"
or
"i've seen better heads in a p*ss trough".
oh, here's one to describe how fair / white someones skin is.....
"Geeez, your skin would burn watching the fire works"
for those with fat faces, double chins etc.....
"you'd need a bookmark to find your own collar"
or
"more chins than a Chinese phone book"