The vanilla command block textures have some weird alignment and shading issues:
!Vanilla command block textures
The background pattern of the blocks does not tile properly when blocks are rotated:
!Background pattern on vanilla command block textures
The baked in shading leads to the appearence of light coming from different directions based on the block rotation:
!Shading on vanilla command block textures
The odd-dimensioned panel on each face has alignment issues, even between the front/back panels and some of the side panels on the same block:
!Panel alignment on vanilla command block textures
This resource pack aims to address some of these issues by making the overall texture 32x32 pixels, allowing the panel texture to be centered independently of the background texture. The background texture has been updated slightly to tile more evenly, and block states have been updated to use slightly different panel textures based on face orientation:
!Updated command block texture
!Updated background pattern
!Updated light direction
!Updated panel alignment
For a similar texture with a thicker, closer-to-vanilla border around the panel, check out the normal variant on Modrinth.
For another texture that fixes the shading and tiling issues while staying 16x16, check out this resource pack.

