As far as I remember "NewOpcodes by DK22Pac" supports loading custom textures
http://gtaforums.com/topic/518780-cleo4newopcodes-by-dk22pac/
[shcode=cpp]
{$CLEO}
{$I stdc}
if
0D42: load_txd "myTxd" from "MODELS\\FRONTEN2.TXD" // IF and SET
then
0D43: 0@ = txd "myTxd" id
while true
0209: 1@ = random_int_in_ranges 2 9
0AD3: 2@v = format "back%d" 1@
if
0D46: 6@ = find_texture 2@v in_dictionary 0@ // IF and SET
then
32@ = 0
while 32@ < 3000
wait 0
sprite.Draw(6@, 100.0, 100.0, 600.0, 400.0, 255, 255, 255, 200, 0.0)
end
else
wait 0
end
end
end
[/shcode]
but doesn't 087B uses textures from gta3.img? (so if you replace it there, it should load your costume one?)