First up is a great tool for searching for photos using a colour picker wheel.
You slide your way through to a colour you like and hey presto!, the colour you chose suddenly appears from the millions of photos on Flickr, which, if you don't already know, is one of the largest online photo sharing sites in the world. Give it a go here.
Next up is a wonderful tool for making up mosaic walls based on search terms. From this you can create your own badge, as I've done here, to display my own work. Of course, art teachers could use it to create embeds into school webpages or blogs that focus on particular themes.
It's called Photo to Wall and you can try it here.