Here's an interesting free web site for tweaking photos and other images. You'll find it at https://www.photojoiner.net/ and it has a couple of neat tricks up its sleeve.
First, there's a photo editor that lets you rotate, crop and resize images. Plus, it has a whole slew of effects that you can add to your image in order to change the colours. There are settings called Summer, Nordic, Greyscale, Festive and more, for example.
If you have ever wanted to create your own internet meme, there's also a separate meme creator feature too. Add a photo, add a couple of lines of witty text, and take the web by storm!
The site appears to be free to use, including downloading your creations.