I've been using Big Picture mode on a daily basis now, and I have a few more suggestions:
Add a function to follow links posted in a chat massage with Steam Controller; with regular Steam chat I can simply click on a link and it will open with my default browser, but in Big Picture I cannot open these links with my Steam Controller.
Display when user is typing message; when in Big Picture chat, I cannot see when the person I'm speaking with is typing a message like I can in regular Steam chat.
In Big Picture Mode, there isn't an estimated download time.
You're given a percentage, and download speed, but not a estimated time of completion.
Example:
Here's what it looks in the regular Steam interface:
As you can see, in the standard interface, there's the "TIME REMAINING" to indicate when the download will be completed.
Just a small thing that I would like to see.