Below is a growing list of free mockups you can download for your surface pattern designs. All of them require Adobe Photoshop and although some require an email address in order to download the file, many do not.
Also, keep in mind that many of free mockups require attribution or “credit to the designer” in order for you to use them in your portfolio or look book. Finally, these are just a small sample of free mockups on each of these sites. Browse around to find 100s more. Enjoy!

Bolts of Fabric
From Creatsy

Summer Dress
From Pixel Buddha

Picture Frame
On Behance

Pillow & Wallpaper
From FreePik

Beach Chair
From Free PSD Templates

Fabric Swatches
From PixPine

Printed handkerchief
From Raw Pixel

Wallpaper mockup
From Raw Pixel

Totebag
From Creatsy

Totebag 2
From Creatsy

Bed Linens
From Pixel Buddha

Blanket
From FreePik