Emmaitar

is a mod created by Mevans (aka User:LOTRMod) which adds custom paintings to Minecraft. Although it was originally created for use with the Lord of the Rings mod, it can in principle be used in combination with most other mods in Minecraft 1.7.10. The mod is mainly meant for multiplayer, but can also be used with singleplayer if desired. Players will be able to connect to servers running Emmaitar regardless of whether or not they have said mod installed clientside, but they won't be able to see custom paintings without it.

Usage
First, the Emmaitar mod must be downloaded from the GitHub page. For players wishing to see the custom paintings only, that's pretty much it. However, players may wish to install the appropriate NEI plugin so that they know how to easily create beautiful paintings.

If you're a server owner, you and other admins can upload painting images and configure them to be available in-game with specific recipes.

Adding custom paintings
Detailed instructions for server owners regarding how to set up custom paintings are available on the GitHub page.