My most popular free tileset; Celianna’s Tileset. They are free for non-commercial use. Read below for the terms.
Terms of usage:
Can only be used in RPG Maker VX and RPG Maker VX Ace, and in NO other game engine. Can not be redistributed or sold as-is. Can be edited however you want. Edits cannot be redistributed. Only for non-commercial usage.
Interested to use this tileset commercially? Visit the products page to buy a commercial license.
Credit under the name Celianna.
How to use:
Right-click and save the image to your computer. Import them back into RPG Maker VX, or RPG Maker VX Ace and be sure to tick on the “VX compatible” option in the tileset database.
Looking for the old version? You can still download the old version here.