No pun intended, but I had the hardest time finding images of clocks for my first graders when we studied measurement this year. I've created 103 PNG images of clocks set for various times according to Common Core State Standards.
Included in the first-grade set:
*24 analog clocks (hour and half hour)
*24 Roman numeral clocks (hour and half hour)
*24 watches (with no numbers)
As you can see, they get more and more abstract as you go.
Included in the second-grade set:
*20 analog clocks (various five-minute increments for practice)
*11 analog clocks (various quarter to and quarter past times)
If you use these files for your own products, please give me credit and link to my store: