Do you need to edit a photo? Add text or cover a detail? If simple filters are enough you can use with satisfaction Paint.Net, practical and open-source, but at the same time powerful for most household uses.
Paint.net installation and use guide: fribby.net/paintnet/?lang=en
Official page: getpaint.net/
Download Paint.Net for free in the version with web or portable installer:
File
License terms
Permission is hereby granted, free of charge, to any person obtaining a copy of this software (the "Software"), to use the Software without restriction, including the rights to use, copy, publish, and distribute the Software, and to permit persons to whom the Software is furnished to do so.
I run a website where I mirror lots of freeware programs; may I also mirror the "Classic" release of Paint.NET?
Yes, so long as you do not charge for access to your website, you may absolutely do this. Redistribution of the "Classic" release of Paint.NET is permitted so long as it is free-of-charge.