Update README.md

Author: alexellis

README.md

@@ -101,7 +101,10 @@ Place all images in a sub-folder `./images/<post-name>`
 
 Each post should have a background photo picked from free stock photography or provided with a Creative Commons license. Do not pull images in from Google without checking that the usage / license is valid first. Crop the background to a width of 1600 pixels. Use JPEG and aim for 200Kb-280Kb in size when exporting (increase compression)
 
-You can decrease the size further by limiting the "quality" of the JPEG from 100% to something lower.
+You can decrease the size further by limiting the "quality" of the JPEG from 100% to something lower like 70-75%.
+
+* [Pexels](https://www.pexels.com)
+* [Unsplash](https://unsplash.com)
 
 * In-post images and screenshots