clothing mockup t-shirt mockup vibrant backgrounds generative ai rgb clothing mockup t-shirt mockup vibrant backgrounds generative ai rgb editable psd 4k resolution tree branch shadow effects t-shirt design mockup template nature-inspired background blue wall white background realistic mockup apparel mockup fashion design clothing template photorealistic mockup high-quality mockup customizable design graphic design digital mockup creative template shadow play nature elements artistic mockup visual design t-shirt presentation design showcase mockup download professional mockup design inspiration fashion mockup t-shirt display mockup creation design elements mockup resources design tools mockup editing design aesthetics mockup collection design portfolio mockup variety design innovation mockup versatility generative ai