MJC's Academic Integrity policy covers images. It's important always to cite the work of others.
Images, songs, videos, other non-textual works are covered under intellectual property laws, even if they don't have a copyright symbol. If you're looking to use an image, make sure you either use public-domain work (no permission or attribution required) or look for material which is licensed for use (try searching for images licensed through Creative Commons). If you find an image that is not copyright-protected or public domain, you should ask for permission to use the image. In any case, all materials not your own should be cited. That includes images, even if they're public domain or copyright-free.
For instructors and students, in general, images used in a classroom presentation, for a scholarly lecture, or in an unpublished assigned paper, fall under the concept of Fair Use or the TEACH ACT. Fair use is an exception to the exclusive rights granted by copyright. For further information, consult Circular 21 of the United States Copyright Office. So you don't necessarily need to ask for permission for this presentation. HOWEVER if you were going to publish this presentation and use it outside the classroom context, you would definitely have to ask for permission to use copyrighted materials.
Keep in mind that if you want to present your image in a PowerPoint, it should be at least 72dpi, and about 1024x768 pixels.
Not all images on Google are copyright friendly. You can locate an image with license to reuse by doing the following:
Your search will be limited to only those images that meet the licensing requirements selected.
Your image source should be attributed with both in-text citation (usually in the form of a caption) as well as a corresponding entry in your References list to maintain academic integrity, even when you use a copyright free image that specifically says no attribution required.
A reader should not have to refer to the text to understand the image. Explanatory text should include title, owner/artist and where the image is stored. In APA you must provide a copyright attribution in addition to citing item when you reproduce it in the body of your work. Clip art or stock images are covered in the seventh edition APA Style manuals in the Publication Manual Sections 12.14 to 12.18 and the Concise Guide Section 10.12.
In general, citing images can be complex. But don't fret; just do the best you can. Find photographer or artist's name; a date the photo was taken or when the image was created; where the original is stored; and where you found it (URL or publication information). Construct a citation as best as you can with that information.