Hi and welcome to a.org :-)
There are loads of options for an A1200. You could just get an accelerator which will fit in the desktop case and make everything a lot faster. You can add USB ports with the Subway card. You can put the A1200 motherboard in a tower and add CD-ROM drives, more hard drives, SCSI interfaces, and even PCI slots, which then allow you to use graphics cards, sound cards, network cards........
As you can see the possibilites are endless. Have fun!
--
moto