Oldfags are typically anonymous people on 4chan and other imageboards ect. who claim to have some greater understanding of the site, or expect some form of respect for their seniority. Ironically, since no one cares about anonymous individuals you can never tell if the person is being truthful about this or not.

They typically are very conservative, and protective of "their" site, aggressively voicing their disapproval of any form of change. On 4chan this is common enough that it has virtually become a type of trolling. It can be assumed that not all people claiming to be oldfags are actually oldfags, but in reality trolls trying to start up drama or flame war threads for attention, or even just for "lulz". This image can be used to call out such individuals, and spread sentiment that change is constant whether they like it or not. Oldfagging is something that can never truly be stopped and will most likely continue into the decades. The actual image is a purposely terrible ms paint depiction of a typical oldfag, including a neckbeard and trollish face.