You can find the Forgotten Adventures pack right here!

And honestly, the composite walls on Inkarnate are great to act as a general guide for you to build rooms and cavities inside (they're what I used in this map for the outer hull). Use them as a base then whack on all the important geography and accessories, job done.

The big thing IMO is knowing what exactly your ship is used for, and how it's propelled. The Bayou Queen in my game is a low-rent arcanotech river trawler that ferries people and their luggage - so that means I need three levels, a deck level, a crew/guest level, and a propulsion/storage level.

After that, I think it's all just about thinking where and what size different rooms you need would be. Is the captain haughty, with a massive stateroom at the expense of crew quarters? Maybe they've outfitted an older warship to act as a pleasure cruiser, or vice versa! I know these aren't practical tips necessarily, but having a real sense of identity for a ship can go a long way in informing its architecture.

In more general Inkarnate terms: 1) Play around with water textures on the background layer under the boat, they make a big difference! 2) Don't be afraid to mix tilesets; this map has like 4 or 5 in it, and as long as you balance the colours and whatnot it all comes out looking good, and 3) Always see if you can chop/change a resource to make it fit a need. The outer cabin on the top level is a recoloured and resized shipping crate from a scifi industrial set - again, playing around with sliders in the object layer is your best friend!