Copyright and data privacy
Copyright
Whenever you use files not created by yourself, for example images or videos, the copyright must be considered.
Using a file or even a text without proper copyright lead to high fines. If in doubt, do not use a content without consulting legal advice first.
Even images that you created yourself might infringe someones copyright. For example you may not take pictures of certain artwork or draw a picture of your favorite cartoon character and publish it.
Have a look at the related Wikipedia article: Copyright
Data privacy
In different countries there are different laws about data privacy. In general, you may not publish pictures of or data from any person alive or dead unless the person consented. There are some exceptions for persons of public interest such as politicians, scientists or movie stars.
Personal data does not only include a persons name but each information that might help to identify the person in question such as phone number, email address, IP address, nick names, pictures, car license plates etc.
Wikipedia has a good article on Personal Data which explains the situation in different countries.
Publishing personal information without consent might lead to high fines in some countries. If in doubt, do not use any personal information without consulting legal advice first.