The Actipro Icons Elements set is professionally-designed in the Metro (Office 2016) style and includes over 1,700 overlay elements.
Many elements come in multiple sizes, everything from 16x16 up to 64x64. Combine an appropriately sized element with your own icons.
The largest elements in the preview above are intended to be combined in the corners of normal full 64x64 icons, while the smallest elements above are made for use with 16x16 icons.
This partial assortment of 32x32 size elements shows the variety of icon designs.