I'll bet if you sent an email to one one those people that post the pictures they might be nice enough to answer you and maybe even tell you what program they use (dont' worry it's free) and how they do it.

how 2 get rid of the HUD in 5 easy steps

1 take your screenshot
2 get scissors and cut all offending parts off of said pic
3 get a large mallet and use it to bash 7 green hats
4 look out the window for a while
5 Paint.exe has performed an illegal operation and will now f*ck up

see,done now