For instance, if I want to make a minifig of my Minecraft skin, I want some kind of program to do that.
I believe that Studio PartDesigner can do that.
As an alternative to Hugo's suggestion of Studio Part Designer you might want to try Mecabricks. I find Studio easier to work with in many cases because it is a native application. Both tools allow you to model with LEGO parts and get great 3D renders of the models.
Mecabricks excels in having more parts available. With Studio there are more cases where you need to use the customization tools just to get a stock part while Mecabricks will already have the part. I found this while working on custom minifigs, but I wouldn't be surprised if it applied to other categories of parts.
It can be more challenging to get started with Mecabricks, but they have some good tutorials pinned in their forum.