This picture shows the Ipevo Point 2 View USB document camera connected to my Chromebook. The Ipevo is a cost effective little device that can be purchased for around $70. There are also a number of optional accessories like a magnifying lens, a microscope adapter or a height extension stand. Check it out here: http://www.ipevo.com/prods/Point-2-View-USB-Camera.
You can also use any other document camera that can be connected to your Chromebook via USB.
I like to use an app called Webcam Toy to display the image on my Chromebook. (You can also use the native Camera app on your Chromebook by changing the camera settings to display through an external camera instead of the internal camera. The camera settings are a bit tricky to find: look under Settings > Show advanced settings > Privacy - Content settings > Media - Camera.) Whichever camera you decide to use, snap away and capture images.
You can even do a screencast - that's right, capture video. Screencastify is a video screen capture tool for Chrome. Record your entire desktop or just a tab in your browser. You can save to disk or upload to Google Drive or YouTube.
Need to conduct a demonstration or show small things to a big audience? Connect your Chromebook to a projector or fire up the Google Cast extension and display your content on your Chromecast device from your browser.