Would need new art. I'm not an artist. Original mod author I /think/ made the current art based on old (0.1x?) Factorio sprites. I /might/ be able to update them to be based off the newer (1.0? 1.1?) sprites, but as is, there's still only one the direction for the regular vanilla solar panels... :-/
Neighbor bonus is a bit weird. So right now, if you hookup a grid of panels and only pull off of one of them, they basically get a bonus. If you pull from more than one, it divides and does a negative bonus! D-:
If you could either join the discord and drop a screenshot of your setup or report an issue on github with a screenshot, that'd help me a bit about how you expect neighbor bonus to work for your setup. I can't promise I can make it work, but I can at least look into it.