Just call this URL to get a random image.
https://placeholderimage.eu/img
Just add Widh/Height values to get resized image.
https://placeholderimage.eu/img/800/600
Get a random image from a specific category by adding {categorie} at the url end
https://placeholderimage.eu/img/800/600/nature
Get a specific image from a category by adding {categorie}/{identifiant} at the url end
https://placeholderimage.eu/img/800/600/city/1
For each category, you have 15 differents images (ID 1 - 15)
Add image filter by adding {filtre} at the url end
https://placeholderimage.eu/img/800/600/animal/1/greyscale
https://placeholderimage.eu/img/800/greyscale
https://placeholderimage.eu/img/greyscale