From my experience,to run Nopcommerce by IIS two thing we have to Check

1.Check
<connectionStrings>
       <add name="LocalSqlServer"
        connectionString="data source=.\[SQLSREVER Instance Name Of the host ];Integrated
        Security=SSPI;AttachDBFilename=|DataDirectory|aspnetdb.mdf;User
        Instance=true"
        providerName="System.Data.SqlClient"/>
        </connectionStrings>

     present in machine config file of the host.

2.Write permission to images/thumb folder.

If you get error like this:

No.1:

An error occurred during the processing of a
configuration file required to service this request. Please review the
specific error details below and modify your configuration file appropriately.

Parser Error Message: The connection name 'LocalSqlServer' was not
found in the applications configuration or the connection string is empty.

then  it may cause for no.1.

No.2:

A generic error occurred in GDI+. Description: An unhandled exception
occurred during the execution of the current web request. Please review the
stack trace for more information about the error and where it originated in
the code.

Exception Details: System.Runtime.InteropServices.ExternalException: A generic
error occurred in GDI+.

then it may cause for no.2.


Good Luck!