I have been making many sets of custom ‘tweets of love’ tiny note cards for the fall STS. When folded they measure 2" by 2". One of the things I enjoyed about these was seeing which birds were picked and what colors they wanted for their birds.
These are stylized English robins:
More robins:
I made about 4 sets of robins, but don’t have pics for them all.
The first three are stylized carolina wren, warbler, and red breasted nuthatch
I love the set of robins that I claimed! They are great little gift-enclosure cards; have already used some. The super-whimsical ones are also adorable!