http://www.uploadit.org is the one I use nowadays for my sig. After freepixhosting shut down I needed something else and this was the one that popped up in my head. It's likely someone named it already, because usually I wouldn't know where to find services like this.
However, I don't know whether you could use this one to post large pictures.
EDIT: files can be no bigger than 200kb and it has a maximum of 20 pics. If you pay 5 GBP a year, you get a lot more.