Well, the thing is, if you want to create a 4096 skin, you will need to double the size/rez of the 2048 and then repaint the TGA as the enlarging process will blur the details but it could be used as a template. If you just resize the TGA files, you will not get a higher rez, it needs repainting.
As for the 2048 skins from GW, I have those as a separate pack (VIIB/C & IXB/C/D2), the Type 2 & 21 will require repackng of their DAT files and as such I never bothered, partly due to the fact I never use them but can certainly extract and upload them. You will, however, need to pack them into the respective DAT for your version of the game.
VII Textures (2048) -
HERE
IX Textures (2048) -
HERE
These are packed into JSGME ready folders, just enable & go.
Thanks & Credit go to Fubar who originally created these for GW.
Top work.