Find IDs from a list that don't exist in a table
You can use an outer join against a values list (similar to Martin's answer mentioned above):

select t.id
from (
  values (4),(5),(6) 
) as t(id)
  left join images i on i.id = t.id
where i.id is null;


or a not exists together with the row constructor:

select *
from ( 
   values (4),(5),(6)
) as v(id)
where not exists (select *
                  from images i
                  where i.id = v.id);


If you like you can also put the values clause into a CTE to make the final query easier to read:

with v (id) as (
 values (4),(5),(6)
)
select v.id
from v
  left join images i on i.id = v.id
where i.id is null;