The Lesser Ritual of the Pentagram traditionally involves calling upon beings associated with the four cardinal points and the four elements. In the original Golden Dawn ritual these were the four archangels, Raphael, Uriel, Gabriel and Michael (east/air, north/earth, west/water, and south/fire, respectively).
Now, there's almost an endless amount possibilities for these four guardians. They could basically be any four entities that please you, in some way. I have related some, both from mythology and popular culture, that I've occasionally used in the LRP's I've written up here. The G∴D∴ ritual calls upon these beings after the pentagrams have been traced (using Hebrew names of God during the tracing), but I usually favour a simplified form which calls only upon four names.
Here are just a few possibilities based on mythologies and occult sources:
The four winds of Greek myth (the Anemoi): Euros, Boreas, Zephyros, Notos.
The four symbols or constellations of East Asian philosophy. I find the Japanese names easier to pronounce than Chinese: Seiryuu, Genbu, Byakko, Suzaku. The Chinese elements, of course, differ a little from the western tradition. The usual associations are with wood, water, metal and fire, respectively. It would not be a great leap, however, to interpret wood in this context as air and metal as earth. This leaves water and earth reversed in comparison with the G∴D∴ system, however.
'The Art Theurgia Goetia', the second part of the Lesser Key of Solomon, lists spirits associated with points of the compass. Their rulers, associated with the cardinal points, are: Carnesiel, Demoriel, Amenadiel, Caspiel. While the text itself doesn't speak much of the elements, but there is a diagram which indicates association with air, water, earth and fire, respectively. Interestingly, these associations are similar to the Asian constellations. These names have the advantage of being based on old grimoire tradition, yet more neutral than angels or demons.
An interesting 'family tree' from Greek mythology, from eldest to youngest: Chaos, Nyx, Eris, Atë. (The first three should require little explanation. Atë is the goddess of ruin and delusion, a daughter of Eris according to Hesiod.)