First have you cycled the tank (read the section in the beginners bit about how to properly do this)
If you have or once you have then you are fairly limited by size. A Betta is the obvious suggestion, with some dwarf cories 'habrosus' or Otos. Maybe some shrimp.
It's a pretty cool calculator for fish stocks. There's plenty of other apps there too.
PS. 35 litre = 7.7 UK gallon tank less space taken up by gravel, filter etc and of course that's only if you fill it right to the brim. Which I hope you don't!