Only describing postgres tables with "\d" (not sequences, indexes, views, ...)
How about simply using the \dt command? It's here to list tables only. You can get more help on PostgreSQL inner commands by issuing the \? command.

If you want to know what those commands do behind the scenes, you could also start psql with the -E option, as asked here. You could therefore rewrite this query to get exactly what you want, be it views, sequences, tables... or any combination of the above.