It's not random, it is calculated by the client. Last time I checked the function was:
Code:
if (map_id == 0x20) {
*(undefined4 *)(param_1 + 0x51) = 0x55521e24;
}
else {
if (map_id == 0x40) {
*(undefined4 *)(param_1 + 0x51) = 0x55521e25;
}
else {
if (map_id == 0x60) {
*(undefined4 *)(param_1 + 0x51) = 0x55521e26;
}
else {
if (map_id == 0x80) {
*(undefined4 *)(param_1 + 0x51) = 0x55521e27;
}
else {
if (map_id == 0xc0) {
*(undefined4 *)(param_1 + 0x51) = 0x55521e23;
}
else {
*(int *)(param_1 + 0x51) = map_id + 0x5551d000;
}
}
}
}
}
with *(undefined4 *)(param_1 + 0x51) being the image ID
So if your map_id is 12345, the image ID needs to be 1 431 437 369