It depends on where the designs come from and what rights they carry.

• Copyrighted designs (like artwork, templates, or graphics someone else made) usually can’t be used in your yearbook without permission or a license, since that would be copyright infringement.
• Royalty-free or Creative Commons designs may be used, but you need to carefully check the license—some allow free use with attribution, others restrict commercial use, and some forbid modifications.
• Purchased designs (from stock image or design sites) are usually safe to use in a yearbook as long as the license covers print projects.
• Public domain designs (works with expired copyright or those the creator released to the public domain) are safe to use without restriction.

If your yearbook is being printed and sold, it counts as a commercial use, so you need to make sure the license explicitly allows that.