Starting with TablePress 0.9-RC, the sorting and pagination arrow icons in a table are loaded from the great Font Awesome icon font. This not only guarantees high quality icons, also on HiDPI/Retina screens, but it also makes the icons more customizable and faster to load.
A minor drawback is that this feature is not supported by the very old Internet Explorer 7. Given then low market share of this outdated and insecure browser version, this is usually no problem. Some people however require compatibility of their sites with IE 7 (You have my condolences.). These people can install this Extension (just like a regular WordPress plugin), which will restore loading the sorting and pagination icons from image files, which is supported in IE 7. Please note, that you really should only install this if you really need IE 7 compatibility. Going forward, this will likely not be supported.
If this Extension is helpful for you, please consider supporting further TablePress development with a donation. Thank you!