Length functions and reduced words for complex reflection groups (M. Cohen)
Hyperbolic Coxeter groups (C. Egedy)
Quaternionic reflection groups
Special representations
Braid groups (A. Lowrance) There are many, many other papers on braid groups that would also make suitable topics for a talk. This one in particular, however, is important for us because its main result is the motivation for the definition of the Hecke algebra of a complex reflection group.
Knot and link invariants (G. Pruidze)
“Coxeter-type” presentations for complex reflection groups (J. Culbertson)
“Crystallographic” root systems for complex reflection groups Recall that crystallographicity is an integrality condition on the root system. The fascinating idea in this paper is that if we replace Z by the ring of algebraic integers in a suitable number field, then all complex reflection groups, including all finite Coxeter groups, may be thought of “crystallographic.”
Other topics . . .
The last chapter of Humphreys' book is a brief summary of a number of interesting topics that one can explore starting from a basic knowledge of Coxeter groups. Any one of these would make a suitable topic for a talk. You would probably want get a bit deeper into the subject than what's in Humphreys' book, but he provides a good list of references for each topic.

The word problem (S. Gaudet)
Reflection groups in Lie theory (M. Laubinger)