Maps are best at the power of 2
256x256
512x512
1024x1024
2048x2048
4096x4096
8192x8192

These are the 3D industry standards.

What you can do (examples) is use one size for the diffuse map, and another size for the Displacement map, and et another size for a transmap
But for any size, stick to the power of 2 rule as above.

Best regards, Tony

Poser 1, 2, 3, 4, 5, 7, P8 and PPro2010, P9 and PP2012, P10 and PP2014 Game Dev
"Do not drive faster then your angel can fly"!