You might want to checkout Holder.js, it is much like placehold.it but client-side.

http://imsky.github.com/holder/

Twitter Bootstrap recently Replaced Placehold.it with Holder.js, a client-side and retina-ready placeholder image tool.

Alternatively, if you're just looking for a way to put placeholders on a page, image services and javascript solutions seem like overkill. You can achieve the same thing with a bit of css:

https://github.com/adamsanderson/placeholder

If you aren't looking for realism, robohash.org is fun

Great resource. This can prove helpful for quick comping or prototyping, but I wouldn't present these placeholder photos to a client.