The current goal is to HiDPI/2x current assets, whether that’s through making new versions of various images/icons or converting to CSS solutions (pretty much gradients and perhaps comment bubbles). Longer-term we may end up using other solutions, but for the moment let’s focus on the task at hand.
I’ve left a long comment about things I’m seeing as still needed. No need to know how to do the CSS patching – a dev can jump in and do that part if you’re more comfortable with the graphics side. What we need is people helping out with creating 2x versions of things, sometimes in various colors. We may need to coordinate with @empireoflight (Ben) to make sure there’s no duplicate effort.
You’ll want to be uploading files to Trac for the most part – if you want to have somebody take a look first, feel free to post a comment here or talk about it in IRC (office hours are a great time for that). Note that uploading files to Trac does not trigger an email notification, so you’ll want to leave a comment noting what you’ve added so it’s not overlooked. Again, feel free to ask questions here or in IRC if you’re not sure what to do and we’ll try to get you sorted!