Only the 1.8 version is posted here, a 1.7.10 version is availalable at hdmcs.co

About:

This mod allows Minecraft to use 128x, 256x, 512x, 1024x player skins in addition to the default size of 64x. Any players using the mod are able to see higher resolution skins on other players that have them, while those without the mod are shown normally.

Installing the mod:

Install Forge, then drop HDSkinsCore.jar (unzip from HDSkinsCore.zip, I can't upload .jar files directly) into your /mods folder.

Using the mod:

If you only want to see other player's skins just install the mod. If you want your own HD skin, go to hdmcs.co

If you are using Minecrfat 1.8, you will also need to clear the game's skin cache to see any new skins. To do this
go to your .minecraft/assets/skins folder and delete everything there.

Known bugs:
Player heads (the item, not on the actual player) don't always work.

Want up to the minute info on the status of the mod, along with occasionally some other topics? Then follow me (@angrykhan) on twitter!

Disclaimer:

THIS MOD IS PROVIDED 'AS IS' WITH NO WARRANTIES, IMPLIED OR OTHERWISE. THE OWNER OF THIS MOD TAKES NO RESPONSIBILITY FOR ANY DAMAGES INCURRED FROM THE USE OF THIS MOD. THIS MOD ALTERS FUNDAMENTAL PARTS OF THE MINECRAFT GAME, PARTS OF MINECRAFT MAY NOT WORK WITH THIS MOD INSTALLED. ALL DAMAGES CAUSED FROM THE USE OR MISUSE OF THIS MOD FALL ON THE USER.