New mockups. Changes as follows:

On SpecialCreateCollaborationHub:

• Image and colour selector floated left of both title and display name inputs, which in turn should be lined up to introduction input
• Image selector displays default image before another image is selected (also needs implementing)

On CollaborationHubContentEditor, with image selected:

• Image width remains constant regardless of height
• Limit displayed height to maximum... 200px, maybe?
• Whitespace is unfortunate, especially with taller images, but not sensibly avoidable. May be mitigated by using this space later for further options.

In general:

• Changes, widths, etc the same regardless of which form it appears on
• Preview width: 150px
• Preview border: both images and colours - #a2a9b1 (?!) to match ooui theme; also slight border radius
  • #72777d on hover/active
• Icon background (false button): #fff; 75% opacity
  • 90% opacity on hover/active
  • slight rounded corner on image selector icon background (non-border corner)
• May just set icons for both image and colour to magnifying glass 'search', as both are selects
• Entire preview serves as button; clicking toggled popups
• Horizontal distance between theme block and title/display name inputs should match standard vertical distance between labelled form elements
• Either add a tooltip for the colour, or get rid of tooltip for image, too, and replace with a tooltip with information about the theme in general, and the selection for both
• New label for 'Hub theme' unique to js mode for selector toggles; does not appear on flat form