I think the dither pattern icons would look better if you displayed the repeating units exactly instead of extending them to symmetrical rosettes, which confuses both dot density and dither pattern size:

You would allow dithering patterns of sizes other than 4 by 4 to be displayed without confusion about their size:

Different alignments of the "same" pattern would be clearly distinct:

A generalized display of dither patterns would allow loading them from a library of tiny image files and/or grabbing them from the canvas instead of providing a fixed and very limited set.