Front teeth crowns are short, big and wide. Can I reshape these without taking off the crowns? (Photo)

They do look pretty wide.  Not much you can do other than replace them.  From the photos the case would turn out much nicer if you did four teeth as opposed to two.  Best of luck.  

Hi:You can have your dentist do limited adjustments to see if the apprearance can be improved.  If not, I suggest to redo the two crowns and also do two veneers on the adjacent two teeth to make all four front teeth more proportional.  Best,Dr. Maddahi

It is not a good idea to reshape the existing crowns as it is not going to look correct.  You will want to consider doing the front six teeth to get proper symmetry and harmony.