How about an activity indicator? Framework 7 has a nice one. The F7 Preloader is made with SVG and animated with CSS so it can be easily resized.
Default
Color Preloaders
Multi-color (MD-theme only)
Preloader Modals
With app.preloader.show() you can show small overlay with preloader indicator.
With app.dialog.preloader() you can show dialog modal with preloader indicator.
With app.dialog.preloader('My text...') you can show dialog preloader modal with custom title.