Photobie is one of these options. It is a tool to edit images that includes many practical functions, that can range from modifying the size of a photo to the creation of animations using the GIF format.
The program has a large collection of filters, that can be expanded by means of third party developments. One of the most appealing tools that the program includes is, without a doubt, the 3D image converter tool, that will allow us to create cubes, spheres, or any other figure from a photo.
With regard to the interface, it is necessary to say that it isn't as intuitive as that of other editors, because it has many menus and not all the functions are easily accessible.
If you are looking for a free editor that has many practical functions, you at least give Photobie a try.