More farm stuff like horses and baby animals
I'd like to see some animation. Everything is just flat and boring. Give us some movement for Pete's sake! Flags that wave, water that moves, etc. I played a differnt farm type game and all the amimals moved a bit and even fell asleep!
I'm not much for themes, but I like the idea of old fashioned stuff.
As a theme - or idea ... How about trains. You could have various types of train stations. Old fashioned/turn of the century or modern. Change them with the season (harvest time have a number of the crops shown on the platform-winter could have, snow) . The locomotives again could be modern or old fashioned. Tracks could be like the various paths (cobblestone, etc) that you could weave around your farm.