Just look at indie games which got released and you will find out that they rarely have sprites exceeding 32 pixels.
I doesn't matter really what released and sucessful pixel art games we are talking about, the resolution is about the same size for all of them. And it's in all of them significantly smaller than 64px height.
Undertale, Hyper Light Drifter, Nuclear Throne, Stardew Valley, Hotline Miami, Axiom Verge, Enter the Gungeon, Shovel Knight, Towerfall etc.
Grab some of their sprites and put them next to your stuff.
All of those games were made by guys who knew how to finish games and they knew if they would go bigger with their resolution, their game would get nearly impossible to finish off in a realistic development cycle of let's say 3-5 years.
I mean... it's not really the reslution which limits you.
design and visual style are much more important.
How many pixel art games with a charsize of about 200px are out there? I don't kow for sure, but probably a dozen of really high quality fighting games mde by capcom and SNK at the pinnacle of their company carrer, supported by artteams of multiple dozens artists.