How to change the DashboardSettings of maximum controls limit in Dynamics 

The maximum number of controls allowed on CRM2011, CRM 2013 Or CRM2015 dashboards is 6. You cannot put the more than 6 graphs/charts/iframes/web resources etc. on the dashboard.
We can extend the number of controls as per the user needs. This setting is applied to the server not a organization setting. So you cannot change this setting for CRM Online but you can change this for an on-premise installation.

1. Open the Windows Power Shell command window
2. Add the Microsoft Dynamics CRM PowerShell snap-in using

Add-PSSnapin Microsoft.Crm.PowerShell
Sometimes You may get the message saying something like “Add-PSSnapin : Cannot add Windows PowerShell snap-in Microsoft.Crm.PowerShell because it is already added.” It is fine no problem.
3.  Run the following 3 commands
$setting = Get-CrmSetting -SettingType DashboardSettings
$setting.MaximumControlsLimit = 10
Set-CrmSetting -Setting $setting
After that open CRM, still you will be see only 6 components on the dashboard design, however you can add extra components based on how much you have set the limit.
Once you crossed the limit you will get following error message.

Note the maximum is 20