I like the albatross in VDT because it whispers to Lucy, sort of lets her know, specially, that it is Aslan. Lucy always has a heightened connection to Aslan, and the albatross is a good illustration of it.
Lewis said VDT was symbolic of "the spiritual life (especially in Reepicheep)," so perhaps the appearance of Aslan in so many varying ways — many different ways except in his true Lion form — is a symbol of how, in our spiritual lives, we do not have Jesus in physical form to stand beside us, but we have the expression of His love and power in many different ways: the Word and Sacrament, of course, but also in the encouragement and prayers of our friends, the writings of those who went before us like CSL and JRRT, and other ways, small signs of His care, godly advice from someone else ...
Aslan is always there, even if not in the form we recognize.