Whitening on bottom teeth don't match the color of the veneers on my top teeth. What can I do? (photos)

Looks like when your upper veneers were placed the lower teeth shade was not taken into careful consideration. Lower teeth are statistically more "stubborn" to whitening process therefore one needs to carefully moderate the degree of white shade while restoring the opposing arch...  Keep using your whitening process for longer time, but if unsuccessful then lower veneers are the way to compensate.. 

This can sometimes be a problem with very white veneers. You either need to veneer the lowers or you might try some take home whitening like Opalescence from your dentist. They can make a custom whitening tray that you use for 2-3 hours per day for 4-5 days to see if you can get any whiter.

Too bad they were done too white.
Either you do more veneers on the bottom or ask your dentist to change the top ones to a more natural shade, matching your lower teeth. You should not have accepted them prior cementing them because the difference in color is too great, unfortunately .

Hi:Unfortunately the color difference between your lower vs. your upper teeth is too great to be matched with whitening only.  At some point you need to get lower porcelain teeth in order to match the top.Best,Dr. Maddahi