I need ideas from graphic designer friends.

[HaveAGoodLuck]

Hello, I use intermediate level Photoshop and Illustrator, and I'm grateful to have learned how to use them. I sell phone accessories for e-commerce. I will be introducing printed products soon. I am looking for websites where I can find vectors, PSD files, and illustrations that can be printed. I am searching for both paid and free sites. I am planning to sign up for a membership, but I am not sure which sites are good. If anyone knowledgeable can recommend websites where I can find such drawings, I will sign up for membership. Thank you in advance to those who respond and provide assistance. The products I print on include MUGS, CUPS, PEN HOLDERS, ASHTRAYS, COASTER, T-SHIRT, and PILLOW.