You can print copies of pictures you see on Facebook, however how large they print will depend of the size of the picture that was uploaded by the page owner.
If you just right-click on the picture and choose Print Picture you will get a small picture as Facebook has reduced it to a thumbnail (small) size so the pages can load more quickly for you.
If you want the picture to print larger click the picture and it will pop-up in a larger size. Now if you right-click on the picture and choose Print Picture in the pop-up menu you will get a larger image if the owner of the Facebook page had loaded a higher size file.
After you choose Print Picture either way, your Print Box will appear where you choose the printer and number of copies and other information that you normally encounter when printing things in Windows.