All of my "scrapped" ideas that I can think of at the moment were pretty embarrassing things that I came up with when I was younger. The one scrapped idea I can think of is a world where children are now in charge now that adults had disappeared I didn't really feel a connection to it.It's been done many times before anyways.
I do have ideas that I don't know what to do with/holding off until I get my first series established or completed-
One is a more comedic (yet potentially heartbreaking) tale of two rat 'sisters' each a year apart. (Mind you, that's a big difference in rat years). There's the perky, sociable Delilah and the cynical, but sensitive Delores.
Then there's this fantasy idea about this warrior who is exiled from her home because her race is nonviolent and she had tried to defend her village while the well-known hero was away. Eventually, she and the hero (who used to be her idol before her absence got her in trouble) team up to defeat monsters together, our protagonist using mostly magic and the other hero using mostly force. There might also be some romance involved with them. Not sure if I'm going back to this.
An older idea I had was about a recently outdated robot assistant teaming up with an autistic mechanic and other outdated robots to stop the latest model of robot assistant from using the chip inside people's heads that let them control the robots to take over their minds. It's a shame that I probably won't do this anytime soon, but I have other stories I'd like to tell first.
A more recent idea is a more gag a week style comic with some story elements about a jack rabbit who thinks he's a jackalope. I'm still working on developing it, but it's not a priority right now.