Change texture resolution

[micheus]

After you have UV mapped your object you should choose the texture size, you know, but after that, if you want to change the texture size you just can replace it with one that respect its proportions. So, you can resize or replace the current one 512x512 for another 1024x1024.

The image size is assigned to UV map in values like 0-100% in which 0-512px means 0.0-1.0, 0-1024px means 0.0-1.0, ...
I'm not sure I'm using the right terms, but I hope you can understand them.