Create SQL identity as primary key?

Simple change to syntax is all that is needed:

 create table ImagenesUsuario (
   idImagen int not null identity(1,1) primary key
 )

By explicitly using the “constraint” keyword, you can give the primary key constraint a particular name rather than depending on SQL Server to auto-assign a name:

 create table ImagenesUsuario (
   idImagen int not null identity(1,1) constraint pk_ImagenesUsario primary key
 )

Add the “CLUSTERED” keyword if that makes the most sense based on your use of the table (i.e., the balance of searches for a particular idImagen and amount of writing outweighs the benefits of clustering the table by some other index).