There are many infographics creators available, including these free, browser-based options. See this article for comparisons of the features of several options.
These are good sources for images. Be sure to download the highest quality available.
Be sure to credit your sources! Check with your professor to find out what kind of source citations are acceptable for your specific project. One option that won't disrupt the flow of your infographic is to use footnotes and include all sources at the bottom.
Below are links to sample infographics, including a "worst" example with detailed explanation of what went wrong.
Faculty, if you're adding an infographic or other visual assignment to your course, feel free to modify and use this rubric.