A picture is worth a thousand words

Knowing that "one picture is worth a thousand words" you'll probably want to use pictures with your students to help get the meaning across. Free images on the web are not that easy to find. You can always ask the author of an image for permission to use their work but some refuse and others just don't answer. As a language teacher, these are the sites I've found most useful:

1) http://hcmc.uvic.ca/clipart/

2) http://www.pdictionary.com/

3) http://openclipart.org/

4) http://tell.fll.purdue.edu/JapanProj//FLClipart/

You can also try to make your own pictures. Maybe you are not an artist (as it is my case) but if your aim is clarity, sure you can do something useful. In case you want to try, you can use the image editor that comes with your computer. For example, on Windows you can use Paint. Moreover, there are some Image Manipulation Programmes that can help you. Fortunately, not all of them cost money. For instance, you can use GIMP, a freely distributed piece of software that you can download, install and use for free.