From wikipedia:
Rider-Waite symbolism
Generally speaking, Waite describes these cups as
strange chalices of vision. They are all up on a cloud,
which may reflect their ungrounded, impractical or
transient nature and the over-imagination or confusion
of the figure conjuring them. Accordingly, they have
been associated with wishful thinking.
There is some dispute as to what the 7 symbols in the
cups mean, but tarotologists have some speculation as to
the meanings. It may be noted that the exact elements of
this vision may be less important than the very act of
conjuring them.
This Card represents self-delusion. Ideas that we need
not worry about the real world because we might win the
lottery.
The cups seem to offer:
* A snake - may represent animal passion and desire.
Alternatively, some consider the snake to represent
powerful transformative knowledge. The snake around The
Magician's waist may offer insight into Waite's
intention with this inclusion herein.
* A treasure horde - probably represents wealth and
abundance.
* A human head - may represent a potential companion
to the seeker (love).
* A castle or tower - may represent power and
stability, or one's native land. (contrast with The
Tower)
* A laurel wreath - most likely represents victory,
honor and status. Note the skull like shadow on the cup
itself, which may point to the great dangers of vanity
and pride (a deadly sin).
* A dragon - in keeping with the christian imagery
of the deck, it is more likely a symbol of evil, anger
and envy, calamity. Today, dragons are mostly associated
with fantasy, the supernatural, magic.
* A shrouded, glowing figurine - may represent the
burning need for the conjurer's self-illumination.
http://en.wikipedia.org/wiki/Seven_of_Cups