I got very very bored, so looked all these up:

How many horses do you see:



Are the lines parallel:



Count the black dots:



How many legs does the elephant have:



Stare at the central do and move your head back and forwards:



30 animals; can you spot them all:





Is it moving or still:



This one's just weird:



The impossible cube:



Which line is longer:





What do you see:



...and a really good one for last: