[catamountalum2004]

Does anyone know of any keyboards and texting software that supports this?

[SpookDroid]

Don't know of any keyboards, but most texting apps will support it (they just attach the image to your text as an MMS). Why would you use PNGs, though, and not GIFs (the common 'standard' for animated stuff on the web)? PNGs will usually be larger files, too.

[catamountalum2004]

some software apps are going away from the old standard of gifs and going to apngs. Apngs are alot more cleaner looking. Apple just went away from gifs in thier messaging app

[SpookDroid]

Ah, so those 'some apps'. Those are native to each app, I'm afraid (Messenger's stock stickers and Hangouts' ones are PNGs I believe), but for keyboards the standard is still GIFs. If sent via text, however (and no, iMessages are NOT texts, but that's a separate discussion), no matter what the format, it'll be sent as a file attachment over MMS.