cgtextures.com has photo textures galore, free membership sign up allows you to download 15 MB of images free each day. They have photos of deck plating available. I use a vector app, but not Inkscape, but as you say doing an intersection of the floor plating image with the plan itself, is how I'd do that in Xara Xtreme.
Another idea would be to force the grid by enabling snap to grid using 1 inch grid, then using multiple deck plate pieces sliced to exactly 1 square inch, I would place, copy, move, rotate and place with your multiple pieces to achieve the complete deck.
Regarding the different furniture pieces you're looking for. Your deckplan looks rather "CAD" like in its simplicity. If kept in that format, I'd go find some CAD symbols of furniture saved in raster or vector format, whichever is easiest to import.
Otherwise go to Dundjinni forums where there are hundreds of map symbols (mostly fantasy) ready to borrow and use in your maps.
Me, I make everything myself and never rely on map objects, but to each their own.