Both beautifully progress bar vector material
UI kit for app by Roman Dosyn
Circuit Board Crafting by Miguel Angel Durán
Colorful loading icons, appear as if they are glowing. This would only work on a black background as it contrasts well with the loading icons.
Upgrade progress by Maciek Butscher in 40 Progress Bar Designs for Inspiration
Progress Bar - by Béla Lajos | #ui
Thermo - the most stunning weather app I've ever seen.