Well there are lots of books about ships, but you could just look for images of "ships of the line" model ships from ships of the end of the 18th century. We also have an index with photos of historic and replica ships here in the Pirates forum.But as long as you look on the internet for ships of the line from the same period you'll find good sources of inspiration.
As for the colourscheme, here you can see a Dutch ship (De Vrijheid) at the battle of Camperdown in 1797.
The colourscheme is rather brown-ish, just like your model (here's a link, the image is quite large).
Though of course with lego it's better to have some different shades of brown.
As you can also see, the gun ports are red on the inside, so when you open yours, it's historically correct!