first of all, thanks for the textures. what is the license you release them under? is gpl 2.0 or later ok?
yes - power of two would be the best. if you choose another resolution than the "original" textures, we have to edit the maps and realign the textures there, too (at least in most cases).
and the most important part, please provide normalmaps like the one you created and maybe also the heightmaps that you used to create the normalmaps.