Put images on template

I’m making a template to submit it in themeforest and i’m wondering if it is possible to put images on it or it’s forbidden !!
I put some images taken from other templates and i think they’re free to use.

Awaiting for your answers

Only if you have the right licenses/permission etc. Even then use placeholders in the downloadable version

Thanks for answering… But how about fullwidth videos ?

If you are unsure of copyrights of the images or videos, better not use them. If you use images or videos on sites like this it is ok .
Free images:

Free videos: