Before getting into the jazz album covers, I wanted to drop this gem. I found a nice selection of cover art by Wilfred Limonious, via Grotesk on his blog at 12ozProphet. This particular reggae compilation from the mid-1980s is ultra-obscure and features Frankie Paul, Papa San, and others.
On a side note, one of the things I admire about 12ozProphet is their design savvy. Most graffiti artists seem relatively uninterested in the larger context of design (of which graffiti is a subset). 12ozProphet not only understands the connection, but they use it to elevate the culture.