Hi.
Here are some sites that offer clipart for free, so long as you do not share it online as your own, use it commercially, etc (common sense really).
You "can" pay for things from the sites by dontaing if you want to, but you are not asked to pay for anything.
http://www.fumira.jp/ This site is in Japanese, but you can probably navigate around it without knowing Japanese if you click the links on the left of the page linked here.
http://illpop.com/school_a27.htm Also in Japanese, but many images that are good and free. Again clicking the images on the left of this page will take you to other pics pages (in the same site)
If you like the look of either of the Japanese sites, but feel it would be too tricky or time-consuming to use them, this is an option to help with that....
Use either Mozilla Firefox or Google Chrome browser - Install "rikaichan" in Firefox or "Rikaikun" in Chrome. Once intalled and activated within the browser (just by clicking on its icon), you can hover you mouse over any Japanese word and it will appear in English (becuase as part of the install of either tool, a dictionary file, only about 5 MB or so, also installs on your PC, and then the tool just refers to the dictionary every time you move your mouse over a Japanese word) Neither tool will interfer with your browser �s normal functions, and both are trusted by the makers of the browsers.
If you want to do that, but it doesn �t seem to go smoothly for you, sned me a message.
Good luck.
A couple of those above are for pre-made flashcards, not just clipart, which is why you have the "option" to donate.