Two things I’d add:

• Make sure you have permission to modify an image or that it falls under fair use. Even when images are under a license that allows reuse, the license doesn’t always allow you to modify an image. Google image search let’s you filter by license type and photos from Unsplash can be freely modified.
• After modifying an image, run it through tinypng.com or a similar tool to reduce the image size.

P.S.: Love your images Kyrie.