jastusa.com  JAST-USA primarily makes and markets adult "dating sims" from Japan.  I think these are Flash games - I only have Lightning Warrior Raidy I and II, so I can only address them specifically.

II has a little "animation" where a scene will alternate between two stills, like a really short .gif would do.  They both have sound, including voice, and are old fashioned dungeon crawls with boss battles to clear the level.  Motion is done using the arrow keys, though the mouse can be used to click arrows on the screen.  There are potions, swords, and armor, but these only show in the inventory for artwork.

Battles are static images of what look to be hand-drawn cels with a little action overlay (like 1960's Batman, but swipes and spell effects instead of the word balloons).  The hallways and rooms are simple boxes - floor/walls/ceiling all done in whatever is natural to the area (bricks for the tower, etc).  There is a text box that tells what happens each round.  If you win, the image of the opponent changes (usually something where some or most of its clothing/armor is removed) but there are no other animations during fights.

Poser images, textures, and backgrounds would make for great artwork for these kinds of games - I am trying to do something like this myself, but I still need to get Flash and see how it actually works.

If you want to see the preview art, LWR is under Shop --> G - Collections.