At the moment, on a CSS heavy profile, you briefly see SpaceHey's default appearance for a moment until the user's custom CSS is encountered by the browser and it overrides it.
Dedicated CSS block in Edit Profile
If there were a dedicated textarea for CSS in the Edit Profile section, the user's custom CSS could be put still after SpaceHey's stylesheet/CSS, but before the </head> or immediately after the <body>, which would stop the above happening.
People could still continue to put their CSS in the existing places if they really wanted to.
I know the above isn't a big deal, and that this isn't a revolutionary idea, but I thought I'd suggest it anyways. xD