'We have midgets' seemed to be a popular phrase with the local strip joint owners around Wenceslas Square last time I was there - nice to see equal opportunities is taken seriously in the Czech Republic!!
HAHAHAHAHA!

I missed that when I was there!
Anyway,
Walking is the best thing, the Czechs have an amazing sense of humor, so there are tonnes of funny statues and things hidden around town. As I say for most people asking this kind of thing, is WALK! I walked tonnes! all over the place. there is the Zikov tower to photograph out of, but the glass is usually really smudged! Its better to photograph the tower from the base (its really funny!) There is a park on the other side of the river, it would be a long(ish) walk from the castle, but its further up stream, at the top is an observatory, AND! a mini eiffel tower, its much better to take snaps out of because there are small open windows that are easyer to take pics from.
There is a monument to the victims of communism at the bottom of the hill too, thats quite a good one to photograph.
Just walk really! OH! and! there is the giant metronome! its further downstream from the castle, its a strange tramride away.! BUT! it used to be the worlds biggest statue and monument to stalin. then they exploded it with dynamite and replaced it with a giant metronome (czech humor again, a metaphor for changing times...).
AND! theres a shopping center with an upside-down man on a horse inside.....
oh, and watchout particularily at night, the moment pickpockets see someone with a camera, you are like a magnet to them (well, thats what I found) so be away!
and non-photography related-
Make sure to visit the Cafe Imperial! its a 10/15 min walk from the center of town, and its the most amazing Hapsburg-era deccorated cafe! FREE DONUGHTS too! its brilliant!
Try avoiding crowds, I found that the best places where the ones without the tourists!