WinampButtonText "[if(winampPlaying)][line('$WINAMP_OUTFILE$', '2')][line('$WINAMP_OUTFILE$', '1')][elseif(winampPaused)]ResumeWinamp[else]StartWinamp![endif]"

;; displays artist and stuff on the label, guess you got that

WINAMP_COVERPATH "%[beforeLast(line('$WINAMP_OUTFILE$','4'), '')]%/.folder.png" ;; strips the .mp3 filename and adds /.folder

;;This bang refreshes the label
!ParseEvars !LabelRefresh CoverLabel CoverOverImage "$WINAMP_COVERPATH$"

i actually use a lua script (suprise, suprise) to check if the image actually exists:
-- wa is some class for winamp stuff, wa.tip is the label that displays the cover art. When the artist/song label changes its text, it runs !luaexec wa:update()

function wa:update() -- update function
lslua.exec("!ParseEvars !SetEvar CurrentCover '$WINAMP_COVERPATH$'") -- save to a evar so i can check if the file exists
if lfs.attributes(evar.CurrentCover) then -- file exists
if evar.CoverOverImage ~= evar.CurrentCover then
lslua.exec("!ParseEvars !LabelRefresh CoverLabel CoverOverImage %[exportedevar('CurrentCover')]%")
end
self.tip:show()
else
self.tip:hide()
end
end