For clarification:
What information needs to be on the page except the data from Wikidata? / Is it that page that would basically be replaced: https://en.wikipedia.org/wiki/Page_that_does_not_exist? And there would be no redirection to full-text search anymore (https://en.wikipedia.org/w/index.php?search=Page+that+does+not+exist&title=Special%3ASearch&go=Go), provided a Wikidata item is found?

Is that heading into the right direction:

In search it would rather look like they have it in the Italian Wikipedia: https://it.wikipedia.org/w/index.php?title=Speciale%3ARicerca&profile=default&search=lydia+pintscher&fulltext=Search - so there is still a fulltext search beside searching items.

Even though I like your draft, I have some things I wanted to point out:
I'd put the language links where they are on the Wikipedia, so there are only the other projects links left. They might need less space.
Also, somehow in my eyes the images are right, but I don't really know why so I can live with images on the left, too :)

So as mentioned before, the placeholder is not going to be part of the search or included in it directly. (Due to the possibility of the search returning multiple items as results.) The placeholder is supposed to be an own page, created by the special page and therefore has it's own url, space etc.
Just to show you how I thought of it from the more technical point, that's what the page looks now (without any design, just as a test to get all the data from Wikibase repo):

The description may still make sense to differentiate items in the search and if we use it there we should use it on the page itself, too. But I see your point that it might be to Wikidata specific, too.

OK, now I get the picture! Although I wonder about the placeholders' use case if the information is not available instantly but after visiting a separate page first. The placeholder is basically mirroring the Wikidata page where it would be a good chance to make users directly aware of and get in touch with Wikidata which would be just one click away either. Of course Wikidata's major problem in that context is the UI but I wonder why not rather put some power into that.

Anyway, just making another suggestion:

I agree with Lucie that the image should probably be on the right side like it is in articles.

I think we should display the description of an item in a given language somewhere. This make the placeholder much more useful. If there're no description we can generate an automated one based on statements.

As per @Lydia_Pintscher's request:

Still, this involves only minimal design and is meant to focus on the plain structure.
Personally, I would not put the picture to the right as this page's content and intention differs from a regular article.
Automated description sounds good to me. A description would definitely make sense and there would be room enough to place it in the header. Just the native Wikidata one is problematic.
Since @Lydia_Pintscher has a specific vision of the article placeholder, I guess she will guide the way regarding design and actual contents of the placeholder.

So, this is the most recent mockup:

I think we can close this now.