There are many excellent websites with pictures of epithelial tissues. Two I particularly like are:
I have my students complete this WebQuest before looking at physical slides under the microscope in class. It helps them get a sense of what they're looking for.
At the top of the document, I state that the links are both on my website. If you have a website, I encourage you to make direct links to these two resources and navigate kids there (otherwise they try typing in the sites and complain when it doesn't come up!). If you do not plan to make direct links, feel free to remove that line! In fact, feel free to modify this whole WebQuest as it suits your class. Enjoy!