I actually had more fun finding applique crochet patterns to decorate the inside lid. Thread crochet is so fiddly that I had some false starts. But I finally settled on some patterns that worked. I don't know if I'll keep the sea turtle in the tin, but he definitely looks cute. The shell comes out kind of rounded by design, so one could add a little batting for a 3-d look.
If you are interested, these the are links to the free crochet patterns I used:
Tiny round fish
http://bunnymummy-jacquie.blogspot.co.uk/2012/06/sail-away-crochet-pattern.html
Long fish
http://mymerrymessylife.com/2012/04/crochet-goldfish-applique-free-crochet-pattern.html
Spiral seashell
http://dascrochetconnection.blogspot.com/p/sea-shell-garland.html
Sea turtle
http://www.ravelry.com/patterns/library/sea-turtle-applique-2
I'm very proud of myself for actually doing the finishing. This is the kind of thing that can live in a drawer for a long time until the finishing mood strikes me! I decided to arrange them with the ABC as the top of one block and the 123 as the top of the other. Then the sides are the rest of the alphabet. The bottoms of each are the remaining number blocks. I stuffed them lightly with poly-fill so they are scrunchy. My eyes are really starting to rebel in the evenings so I think I made tons of mistakes in all those seams. I was trying to stitch by feel and that's really not a good technique. Not sure what I'll do with these. I think a baby could rip them apart so they aren't really toys. I'll just admire them for now.