There are many different controls to customize who has access to what, so Owners and Admins can customize what they share or don't share.
Here are the more common situations:
I can't see a Presentation that somebody else created.
Presentation sharing can be limited to: Yourself, Inside Team, and Inside & Outside Team. Contact the creator/owner of the presentation to have them share it with the appropriate level. More on Presentation Share Settings here.
I can't see the same Orders.
If you are invited to a showroom and don't belong to the Team that owns the showroom, you will not be able to see all the orders in the account by default. You will only have access to your own orders, and these orders will be sent to the Owner's team.
If you belong to a larger team and have access to the same showroom as your teammates, you have the potential to see your teammates' orders in that showroom, but this will ultimately be controlled by the "Can Edit All Orders" permission in the Account User Settings.
I can't see the same Customers.
This is the same as with Orders, described above. Users on different teams don't share Customer information.
I can't edit a Product or its Price.
Your permission has been limited in the Showroom's Team Settings.
I can't upload images.
Same as above.
I can't see the Subscription or Billing pages.
Only users listed as Owner of their Account/Team are able to see and edit Subscription, Billing, and Account User Settings. To be given Owner status, have an existing Owner edit your Account User Settings.