Image editor or cool cam app?

I have been having with Vector Camera and Turbo Pixel

I don't know of any purpose-made ones, so, if you don't mind adjusting the interface for mobile, you can use Krita

You can also add a stroke in the layer styles to have that sticker-like rim (You can't really see it there, so here it is with reverse background)

Disclaimer: using the transform tool is hell with touch, I try moving a control point around to scale and 98% of the time it will rotate the image, 1% will skew it 1% will finally scale it, but maybe there is some trick I'm not aware of

Effects Pro has a bunch of filters. (but is 9yrs old and some will hang)