To make nodebb more accessible for people with no knowledge of css it would be cool if themes could have options to customize colors or at the very least have a few preset theme colors.
selecting one of the options would change the whole color scheme of the theme, kinda like bootswatches for vanilla but added by theme makers.
vanilla and lavander are both kinda preset up for this with the use of variables.less
if you could add a way to select 1 of X amount of variable files you achieve this idea.
this would allow people to get more and easier mileage out of each theme, and help designers trying to make pay themes
this would be the simplest approach i could think of with maybe the long term goal of greater theme customizing kinda like wordpress http://codex.wordpress.org/Appearance_Customize_Screen
Does is slow down page loading ? It is already at 6 seconds.
Hmm, 6 seconds isn't good nor is it bad. Where are you getting this number by the way?
So yeah, it just depends really on what you're trying to accomplish. If you optimize delivery by compressing the image and using a CDN service (optional), you should be okay. Make sure the image isn't huge or more than 2000px in size. Remember the larger the image, the longer it takes for the end user to download.