You may use Vecteezy images for your free promotional items like t-shirts, buttons, calendars, and holiday cards you send to clients, you give out at trade shows, etc. The license you need will depend on the number of copies you will be printing.
Our Free License covers you for up to 50 copies, and attribution is required. If you need to print more than 50 copies and/or do not want to provide attribution, you can upgrade to a Pro License which covers you up to 100,000 copies. If you need to print more than 100,000 copies, then you will need a Pro Extended License.