In my opinion the del Norte does not have the same monumentally significant places as does the Frances, and is a different sort of experience. The Frances is all about the Camino, but on the del Norte, the Camino passes through..
Portugalete is a northern suburb of Bilbao, about 10km from the city centre, useful as a starting-off point the next day. There is an albergue and a church, but nothing remarkable (the bridge is a World Heritage Site, and a fun ride). Castro Urdiales is 28km further, with an albergue by the bull ring and other facilities, but has nothing notable about it, although the plaza by the harbour is nice. Islares is a relaxed little seaside village, 9km further-- I suppose that you can push on to it if you wish.
The scenery is worth it, and some of the seaports have mediaeval quarters (Laredo) worth seeing. Some love the cities (Santander and Gijon) and others of us skate through. Church-going pilgrims will find it more difficult to locate daily evening masses, although it is possible with some looking around and asking (Spanish churches have an interesting approach to the idea of letting anyone know if there are services)-- See if you can check out the cathedral in Mondenedo in Galicia, and the Cistercian monastery in Sobrado dos Monxes. The coastal variations, if the weather is at all decent, are spectacular (as are the beaches, but swimmers must be very careful about the Biscay undertow, which regularly takes swimmers off to the coast of Kerry and justifies a huge expenditure on Guardia Civil search and rescue teams).
Everyone seems to love the albergue in Guemes, and the one in Comillas. As towns, Comillas has one of Gaudi's first buildings, and a palace which justifies a look: the albergue is located right behind a sculpture museum. Santillana del Mar has become a bit of a tourist trap, but at night or first thing in the morning, has a magic to it. Other towns, normally summer resorts for the Spanish, have a certain charm out of season-- Tapia de Casariego, Luarca, Cudillero...
But don't look for another Frances. You won't find it.