Howdy and welcome to Nikonites!!!
The D7100 is indeed a beast of a camera, and will serve you well. For adding images from Flickr, grab the url for the picture, and you can wrap it in the "" tag to get it to show up. There is also a button on the quick reply editor that will let you get it added without messing with codes.
Look for the icon bar like this: [ATTACH=CONFIG]265140._xfImport[/ATTACH]
Specifically: [ATTACH=CONFIG]265141._xfImport[/ATTACH] will allow you to add an image by URL or to have an image uploaded directly to Nikonites.