You can place images, videos, PDF/Word/.TXT files, audio files (.WAV/.MP3) and web URLs to your board. Click 'Upload' button on the toolbar or just drag and drop your files onto the board. To place a web URL, copy and paste the URL you want to use to your board.
After placing your media files/URLs on your board, you can use image/document/audible/web insights if you have an active subscription to Pro plan.