Yeah, you could open ulx_fun.lua and find the part that says
table.insert( gimp_say, "" )
and add after that
_OpenScript("ulx/ulx_gimpsays.lua")
Copy a lua file to the ULX folder and rename it to gimpsays with the extension .lua
Open it, and put this in there, replacing everything else:
table.insert( gimp_say, "INSERT THING TO SAY HERE" )
and put one of those things on every line for every new thing you want to say, EX:
table.insert( gimp_say, "weeee" )
table.insert( gimp_say, "circles" )
table.insert( gimp_say, "yay" )
table.insert( gimp_say, "helooo im nigel thornberreeey" )