Can you ? Yes—but only slightly. The URL trick, browser zoom, and reverse image searches can take you from a 100x100 pixel blur to a 480x480 pixel recognizable image. That is the legal limit.
If you frequently need to see full-size images, certain browser extensions can automate the process. These tools work by pulling the high-resolution source image from Facebook's database that the standard UI hides. view private facebook profile picture better