Another freebie for today is a space grey iMac Pro mockup available in psd format. You can change the screen by using smart layer. To further customize the smart layer first change the existing artwork to 8 bit and then insert your web or UI design. Background is also customizable. File and download details are given below.

Free-Space-Grey-5K-Apple-iMac-Pro-Mockup-PSD

Description:

Available Format: Layered PSD easy smart object insertion
License: Free for personal and commercial use
Zip File Includes: Photoshop PSD File
Mockup Resolution: 5120 x 2880 px
Screen Resolution: 1920 x 1080 px

Instructions:
1. Place your website design on smart layer
2. Photoshop requirement: Adobe Photoshop CS5+

Download iMac Pro Mockup