The Vintage Art collections are exactly what it says on the tin, collections of vintage pieces of art that have fallen into the public domain and as such, may be freely used by people for whatever reason, such as illustration game books or providing reference for an adventure. Now, while you could possibly find many the pieces here if you wished to spend the time, Unza RPG has done it for you and for a reasonable price you get quite a bit of art to use.
Vintage Art Collection: Pirates & Sea has 109 images ranging from ships to sea monsters to sailors and pirates, lots of pirates. While a few of the ships are of the pre-cannon age mostly it shows a view of the 16th-18th century with flintlocks and cannon. Very good if you are looking to illustrate a historically based pirate setting, a bit more limited for others eras.
Disclosure: As a featured reviewer for RPGNow/DriveThroughRPG, I received my copies of these products for free from the publisher for the purpose of this review.
[5 of 5 Stars!]