There’s this site that you can use for testing web designs. When I make a web page I use Lorem Ipsum to fill out the text. This is a typesetting tradition that goes back 6 centuries.
Now if I need an image of a certain size I can place that in the code and use placekitten.com to put the right sized image into my code.
For example, suppose I need a color image about 351×225 in my code. I just use the url http://placekitten.com/351/225 and I get: