Assuming these are panels that can be plastered anywhere that would be convenient, how would spaceship design change?
Would every wall be covered with them so it's all effectively floor space?
Would there need to be special considerations for how the added gravity interacts with whatever propulsion system the ship uses?
How do the panels even work?
Lets assume the most naive idea, that the grav panel is basically a very big floor tile that attracts mass to its "top" side with a vertical vector that runs at a perfectly right angle to the surface of the panel.
Basically, what is above the panel is attracted to it. Things below the panel are not. Things sideways to the panel, even by a millimeter, are not.
Basically, above each panel, there is a theoretically infinite column in which things fall down on the panel, but its potency decreases with distance.
(DISCLAIMER: all of the above is absolutely silly, but this is the only way to have grav-panels that, aside from flagrantly disregarding physics, would not become an impossible engineering headache. Its impossible to have artificial gravity that does not violate physics, but lets alt least have one that conforms to basic common sense.)
So for simplicity's sake, lets assume the grav-panels are 1x1 meter, 1cm thick, and that anything in a realistic distance above them falls on them.
Therefore the most rational design, is to have the spaceship be a long tower, square in cross-section, with its bottom-most floor being covered in grav-panels, while the floors above the panels need not be. This way, most of the ship would be under 1g.
It might make sense to have the guts of the ship (engine, reactor etc) be below the grav-panels, "in the basement" so that they are in 0g (or not, this depends on how the engine and reactor works).
Another thing would be to have a "shaft" going through the ship that has no grav plate at the bottom, so that people and stuff could float up and down it in gentle freefall.
I would not risk putting panels on the walls, especially not opposite to one another. Intersecting gravity fields would play merry hell with the hull structure, and give everyone roller-coaster levels of vertigo, there is not need for that. You want the gravity to go one way and feel seamless between panels, otherwise your crew is going to vomit all over the carpet.
Now the trillion dollar question is: How much power do your grav panels need? And the multi trillion dollar question is, how powerful can you make them?
The reason I'm asking is that if you have artificial gravity plates that need less energy than they can create by making stuff fall down, yo do not need an engine or a reactor. You now have a device that can create its own energy out of nothing, and propel the ship at relativistic speeds. If you can turn a sequence of grav panels quickly one after another, and you stacked them so that their apparent grav field is substantial you can make the whole ship "fall" towards expelled bits of propellant, always missing it.
The same "multi-panel gravity" could very well be used as a weapon, maneuvering thruster (or rather, "puller") and a way to redirect enemy projectiles.
If you make your panels small - think mosaic tiles - and put them on little pivot joints, you can turn every passageway into an automated people mover.
Your crew-members step into the hallway, and state their destination, and the hallway carefully angles and energizes a bunch of panels on the ceiling and walls and floor to redefine "down" as towards your destination. You fall all the way to where ever you are going. (if you start closer to the floor, the ship knows to put more power into the ceiling panels. Once you are in the middle of the hallway, power from all sides is evened out.)
Probably most hallways are zero gee except when a person is transiting them. Express hallways can have the panel direction fixed, so you can only "fall" in one direction - say fore to aft or vice versa. Maybe most travel along the spine of the ship is express, and traveling radially uses more flexible hallways.
Moving cargo around is probably just like the flexible hallways, only you use a bigger space. The cargo hold has lots of mid-size, variable panels and you probably don't actually put things on the "floor." Instead, you use the variable gravity to pull it to where you want, and then use a lattice of steel struts to hold it in place.
Missile launchers, fighter launches, and even kinetic energy weapons can be a variation on the express passage idea. Stuff only moves one way down those particular paths.
The key here is that there's no such thing as a fixed "down." If you can control gravity, down is where ever you want it to be at that moment.
