Quite useful for organising the museum.

Whoa the museum layouts looks great. Thank you!

Updated for the new Tank Manager. Thanks to "anonbc2000" for your contribution.

Now if they could just actually number them like this instead of 3-10 and then 17-20.

Great layout for the Poster slots used it often.
But to move tanks in Tank Manager here's equivalent#:

Poster slots = Tank Manager spots
1 = 3 Tank Manager#
2 = 4 Tank Manager#
3 = 5 Tank Manager#
4 = 6 Tank Manager#
5 = 7 Tank Manager#
6 = 8 Tank Manager#
7 = 9 Tank Manager#
8 = 10 Tank Manager#
9 = 17 Tank Manager#
10 = 18 Tank Manager#
11 = 19 Tank Manager#
12 = 20 Tank Manager#

why ismt there any where to put the big items like MG and Bazookas ?

Well, to be honest this museum layout plan ought to be just a workaround for its missing visualisation in the game UI itself - as a workaround for the developers design flaw.
So hopefully they are going to integrate some kind of layout in to the user interface in the future which would make this museum layout plan obsolete.
But if they don't chances are high I will keep this updated.

Would you be willing to update this if the development team makes changes to the Museum or updates the system? As they have confirmed that they are planning on updating it in the future.

When you fill the museum and display cases, I charge a $10 entry fee and it brings in a whopping $18,000 every 10 minutes. ($ 2,592,000 every 24 hours.)

Great, very useful, thanks!