There are texture packs available for the Creative version of Minecraft and the Survival version; with Survival having the most packs available. First choose a texture pack you want to install and download it. To install the pack, you must have started Minecraft at least once in either the browser or in the client version.

The nicest texture packs can be downloaded on the official forum

Start Minecraft, click on the ‘Mods and Texture Packs’ and then click “Open texture pack folder”. Drag the .zip file from each pack in there and it will appear in the list of textures, ready to launch from the Minecraft menu.

There is one thing though, some textures are in a higher resolution than the original Minecraft, so to use them apply Kahr’s HD texture fix, run it, hit patch and you’re set.