If you just need the text version of the emote and don’t care about emoticon_set, you can avoid hitting emoticon_images entirely by assuming the text contained by the two indices TMI provides you is the text version of the emote.
e.g. if you get @emotes=25:3-8 :fugi!fugi@fugi.tmi.twitch.tv PRIVMSG #twitch :Hi Kappa, you know that message[3:8] contains the text version of emote 25, Kappa.