Someone has probably already posted something like this already, but I've put together a side-by-side comparison of the older (2007-2012) Newgrounds Level Icons and the new (post-redesign) Level Icons. The old icons are from here. I've scaled up the new icons x2; that way all the icons are more similarly sized.
There is a scaled down preview below, the proper version is here.
ColinMan
Cool & interesting