Searching the Web
After performing a Google search, select "quick settings" by selecting the cog button 
to get to the "advanced search." From there, limit to a specific domain, such as .gov, .edu, or .ucsb.edu. Additionally, you can limit by file type. Reports will typically be .pdf files.
You can also try the advanced search on Startpage for some high quality and ad-free results.
Finding Images
Not only can you use graphs and images from online articles (by using a html version and saving), but you can find reliable images from some web sources. Here are some tips for quality images. Please be sure you cite them and note that most of these are Copyrighted and cannot be reproduced on the Internet without permission.
Google Images Sort by image size or color (select "settings" and "advanced search" after performing your initial search)
CalPhotos High quality images from organizations and photographers that usually allow educational use
Getty Images - Sign in for watermark-free images