Your tank sounds too small for nearly everything when full grown. You could go for a crested gecko keep it in there when young and move up to a bigger viv/tank/terrarium when older. The only thing I can think that will fit in more long term are mourning geckos but wouldnt call them a beginner lizard.
As for beginner snakes a cornsnake is always a good first snake and would fit in the tank as a hatchling but I wouldnt call it ideal. Also if you went for anything in that tank you are going to need to change the lid as fish tanks have cable holes in and filter points, all ways you rep could escape especially a snake.
I really think when getting your first rep that you find one you like and think you can look after then buy and design around them rather than trying to fit something in.
Last edited by oakelm; 31-08-2009 at 01:19 PM..