I have been a big fan of Hipstamatic and their lens/film combos. When I saw a devoted tintype app was available I jumped on it immediately but find myself disappointed with the limits imposed (where those same limits are an understood strength in Hipstamatic.) the app launches quickly on my iPhone 6, and I like that I do have some basic adjustments to switch between black and white or colour, the eye intensity and blur strength.
As mentioned, importing files will remove that original image, and theres no ability to choose your square crop. Frames are either on or off, Id like to be able to adjust them especially the heavily imposed colour frame. Choosing the eyes would be nice too. I suppose an app is a balance between function and features, this one, as it currently is, isnt quite enough of the later.