I've extracted objects (JPEGs) from processes` memory dumps (obtained with memdump command from volatility framework) and got strange results after searching the memory pages of the main thread of chrome browser. Some extracted images are very small (212x132 pixels) print-screens of the chrome window, and seem to be taken at random moments, on different sites.
Is it possible to have a trojan that tries to capture browser images, maybe searching for un-sniffable fields (like the ones filled with a virtual keyboard at bank logins)?
If so, why are those print-screens in chrome's memory pages?
Don't have Chrome on this computer, but doesn't it have a new tab behavior that includes clickable thumbnails for sites you have recently visited? If it does I would think those may be the images for that feature.
The answer to all of your questions is "yes it is possible" but that's not to say it's likely. I've noticed a few strange bugs in Chrome, in particular when dealing with Ajax's. What is your operating system? If it's Windows you should definitly have an anti-virus system, no doubt about it. If you do not have one I suggest Avast Home which is free. If you would like a thorough analysis of your system for any malware look to this forum and follow these instructions.