Now that these blocks can be placed on top of glass blocks (in 0.15.90.8 but not in 0.15.10), on top of fences (both 0.15.90.8 and 0.15.10) and on top of pistons (just a bit of the bottom of a block above a piston can be visible when extended), repeaters and comparators need a bottom texture. Even plain stone would be better than the transparent surface they currently have (see two screenshots).

While someone's fixing this part of the texture, it should be easy to fix this one too: MCPE-15806 where pixel alignment is a bit off.

Tested on Samsung Galaxy S6 (SM-G920W8), Android 6.0.1 MCPE 0.15.90.8