The icon will have to be redrawn as an SVG image and added to our LESS styles with the background-image-svg mixin (like, for example, arrow-down-icon.svg). See this bug report for more information. This task is part of larger efforts to make MediaWiki high-density display friendly. This task requires existing graphics skills working with a Vector graphics application (e.g. Inkscape). Links to SVG file(s) that you have created are welcome. For integration, basic knowledge of CSS might also be helpful. Students are required to read Wikimedia's general instructions first.