Whether or not there is a specific sign for "tiny" is debatable. Rather
there are a number of signs that could mean "tiny" (as in "very small").
Regardless, however you sign it, you are going to need to use your face, suck in
your cheeks, and purse your lips. Using your face this way creates a type
of "adverb" that helps change "small" into "very small" (which can mean "tiny").
TINY:
Above I'm doing a version of the sign for TINY using a (slightly modified) "L"
hand (which could also be considered a "wide-G-hand" and changing it into a
"G"-hand.
You could also get this point across by using both index fingers, starting with
them slighly apart and then bringing them very close together.
SMALL-(tiny_short-length):
Also see: SMALL
Notes:
Keep in mind though that "tiny" is relative. I would not use the regular
"TINY" sign if I'm referring to a "tiny" elephant. Instead I'd use a two
handed sign in which both hands are in "FLAT-hand" handshapes that start rather
far apart and then move a bit closer to each other (while using the "tiny"
facial expression).
Notes: