Can you present an image without knowing who originally created it? I would like to present the image located on this website during a presentation I am giving next week. 
http://www.taopatch.com/blog/quantum-dots-entangled-with-single-photons/

The image does not say anything earthshattering, it is well accepted that the structure of a CdSe/CdS core-shell quantum dot is as they depict in the image, but the image does a great job of illustrating it. I do not believe the website was the original creator of the image, after all they refer to a certain paper that was published and in no way reference it. I believe this is the paper: doi:10.1038/nature11573  The image that they use is not in that paper.

edit: Here is another website containing the same image: http://en.rusnano.com/press-centre/news/88604

Can I present this image without knowing where it originally came from? I suppose I could cite the website as a source, but since it appears that they took the image without citing the original creators, I do not want to list them as the source.
Best Case Scenario: As one commented, you can use reverse image search on Google; or just use other search engines and see who created it. If you find it, then you can use the link to the original artist as a reference.

Worst Case Scenario: The good thing is that there is a link for it! So if you couldn't find the graphical artist (the worst case scenario) add the picture and its reference (its related link) in the slide's footnote. To be on the safe side, use the popular link (one of the links on the first page).