This is the second concept shot, and in my opinion, far more interesting than the first. Details on the overall layout, theme, header and footer are described in the first concept.

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User Toolbar
Now that the user is logged in, you can see more options along the bar at the very top. The message count appears as normal. The logout button is at the top-left corner, easy to see.
The tool buttons along the right hand side are all interactive in much the same way as they are in v5, but the addition of a drop-down arrow shows that they can be clicked. Hovering over the buttons will display a tooltip.
The buttons are, from left to right, the main dA menu, where one can access settings, submit deviations and journals, and go to the Help & FAQ and random deviants/deviations. (The menus in the v6 beta are really ugly because the highlighted item is blue, not green, and the bottom corners are rounded, which doesn't look right at all.) The second is a menu for administrators and gallery directors that show various tasks depending on the administrator's role and privileges. The third is the friends box, and the fourth is the collections box, which will cover up the header when expanded.
Having all the tool buttons in one place is not only intuitive to the user as it allows natural exploration of the features, but it also means it's easy to add a new tool in the future.

Advanced Search
Now for the main purpose of the page - advanced search will allow users to construct complex searches for anything they wish, with far greater ease than before. From the left panel, we select what we want to search for, and the interface will change accordingly.
Allowing users to save searches means that not only do their searches travel with them wherever they log on (as opposed to bookmarks), but these searches can be treated as streams for the customizable front page. Perhaps you can even search within a saved search? Hardcore...
Most of the options on this page are already available on the main search, but with an interface, new users will be able to see what they can do without first revising the FAQ. Other options closer to the bottom are not currently available, but they're pretty self-explanatory - they've all been suggested at some point in the past via the Suggestions Forum.
Notice that we also have 'Deviants' on the list. We should be able to search for deviants by matching their real name, complete/partial username match, deviant type, and region in the world. (Not included on the concept: when there is a groups feature on dA, it would be useful to search those too, rather than rely on Club Indexes that are manually updated.)

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See the other concepts: Front Page, Message Center