For versions of Tridon Sites before 9.1
There is no support for displaying SVG images out of the box, either as thumbnails or when working in component view.
As of Tridion Sites 9.1 there is native support for preview of SVG files.
See: Support for previewing SVG (Scalable Vector Graphics) files
https://docs.sdl.com/816112/750876/sdl-tridion-sites-9-5-main-documentation/content-manager-explorer-and-experience-manager-functionality-introduced-in-------------sdl-tridion-sites-9-1