I have completed six-six battleships for the KuK Kriegsmarine and the Regia Marina. They are all scratchbuilt from wooden sticks, broom bristles and plasticard.
There is no strict scale: all of them are approx. 6cm long and 1.5cm wide. Comparing the scale to the Habsburg-class, it is about 1/1900 or 1/2000.
The Italian ships, with a brighter grey hull and brighter decks. As I've said in the previous post, some very interesting ship designs. 3 out of 4 Regina Elena-class ships; both ships of the Regina Margherita class; and an Amiraglio di Saint Bon-class bringing it to six overall.
A standard block-wash-highlight method was used for painting, then I added the name tags and little flags to the base and sealed it with Vallejo acrylic varnish.
The Austro-Hungarian fleet is more uniform with only two ship variants. They are also of a darker color - just for a distinct look.
Most of these ships saw action in World War I, so there is an option to play those, but I'm thinking about a fictional conflict pre 1914, so neither navy would have dreadnoughts.
The rules for naval actions are almost complete - the hyper-simulationist homebrew is not very good for these little ships (there were three charts only for firing, not kidding).