If you're messing with the regular one (not the paperdoll system)...
Let's assume you have a character.  Let's name him...  Fred.  
Why not?  I used Freddy Kruger's first movie music in the demo.   
Now, you normally have a regular character like 001-Fighter_01.png for your character.  Let's give your guy a new character...  'Freddy.png'.  It's nothing special.  We could use '001-Fighter_01', but that's a mouthful.  Easier to just say Freddy.png.
No, it didn't need to be FreddyABS.png.  I just used BillABS in the demo.
Now, the configuration system has this in the defaults:
Code:
# Animation Suffixes ---------------------------------------------------------- 
  SUFFIX_CENTER     = "!"                   # Used for center justified animations
  SUFFIX_MELEE      = "_melee"              # Used for melee attack animations
  SUFFIX_MISSILE    = "_range"              # Used for missile attack animations
and
Code:
# Melee Weapons
#               ID     Range  Mash   Delay     FStart    Kick    Jump    Suffix
# ================     =====  =====  =======   =======   =====   ====    =======            
  MELEE_WEAPONS[34]  = [   2,     3,       3,        1,    nil,   25,   "_sword"]
  MELEE_WEAPONS[5]   = [   2,     1,       3,      nil,    nil,   25,   "_sword"]
Now the 'SUFFIX_MELEE' value is set to '_melee'.   That means that any melee attack performed will show with a character drawn with '_melee' tacked on to the end.   So if you have a "Freddy_melee.png" made up, it will show for any melee attack performed by Fred.  That is... it will show unless you set up special weapons in the MELEE_WEAPONS array.
In the MELEE_WEAPONS array above, you have two weapons defined...  Weapons #5 and #34.  In these cases, it will use a characterset with the '_sword' suffix tacked to the end.
So you could have defined for your Fred character:
"Freddy.png" for his characterset
"Freddy_melee.png" for any melee attack with no specific melee weapons defined.
"Freddy_sword.png" to be used if a weapon is defined in the MELEE_WEAPONS array.
The filename for the attacks and actions is always based upon the name of the characterset in use  (Bill.png -- Bill_melee.png //  Bob.png -- Bob_club.png)
System safeguard:  If a graphic file is not valid, it will not crash the system.  A safeguard in Lycan is that it skips loading missing files rather than crashing as it normally would.