Placeit Apparel - Photorealistic apparel and t-shirt mockups in seconds.
Module 02: Layouts - Professional toolkit for UI/UX design
Mockup Mark - Realistic apparel mockups for ecommerce, social & more
Now UI Kit - A beautiful Bootstrap 4 UI kit. Yours free.
Canva - Canva is a graphic-design platform with a drag-and-drop interface to create print or visual content while providing templates, images, and fonts. Canva makes graphic design more straightforward and accessible regardless of skill level.
Apple Watch UI Kit - Quickly create Apple Watch app prototypes