When using images online – especially for commercial/marketing purposes – you should always:

• Obtain proper licenses or permissions where required. As part of this, make sure to get signed releases for any images using trademarks, logos, identifiable people, or other private entities.
• Respect any terms of use associated with said images.
• Be careful when making fair use determinations. If you’re unsure, seek legal advice.
• When in doubt, seek permission directly from the copyright owner. ...