Question about to place a Elephant in....

[Makanyane]

you're missing two things to get it into campaign game,
1. export_descr_buildings
look for line like

recruit "carthaginian elephant african" 0 requires factions { carthage, } and resource elephants

and change to

recruit "carthaginian elephant african" 0 requires factions { carthage, thrace, } and resource elephants

that makes them recruitable by thrace but only in regions that already have elephants resource. You can delete 'and resource elephants' bit so everywhere can build them (I'd advise deleting map.rwm as well if you change anything to do with resources but confess to becoming a bit confused by that, btw it doesn't hurt to do it anyway)

To leave 'and resource elephants' in, to restrict them to certain regions - as its not a hidden resource i think the one you need to add is to descr_strat, in the top section of that you need line like

resource elephants, 64, 26

but with co-ordinate of a valid point (not in city, on mountain, in sea etc)
for a location in the region that you want to recruit elephants. (its always advisable to find locations before you start other changes - in case you can't then get in to game to find valid locations) Again for this I'd advise deleting map.rwm (hidden resources go in descr_regions, but elephants appear in both and its a while since I changed anything on this!)

Mydraal's

type carthaginian_elephant_crew
skeleton fs_forest_elephant_rider
indiv_range 40
texture carthage, data/models_unit/textures/unit_carthage_light_archer_carthage.tga
texture thrace, data/models_unit/textures/unit_carthage_light_archer_carthage.tga
model_flexi data/models_unit/unit_carthage_archer_high.cas, 15
model_flexi data/models_unit/unit_carthage_archer_med.cas, 30
model_flexi data/models_unit/unit_carthage_archer_low.cas, 40
model_flexi data/models_unit/unit_carthage_archer_lowest.cas, max
model_sprite carthage, 60.0, data/sprites/carthage_carthaginian_elephant_crew_sprite.spr
model_sprite thrace, 60.0, data/sprites/carthage_carthaginian_elephant_crew_sprite.spr
model_tri 400, 0.5f, 0.5f, 0.5f

I think was actually completely workable - elephant's will look exactly like carthages - as using the same existing texture and sprite - there is really no point in copying existing texture, re-naming it and changing texture line in DMB unless you've actually going to re-design / re-colour a new texture which is a whole different tutorial (same applies for sprite).

You can look up mount type in EDU and then refer to DMB, for this it should be elephant_african

type elephant_african
skeleton fs_indian_elephant ; indian is correct, african skeleton is only for cataphract
indiv_range 40
texture carthage, data/models_unit/textures/mount_african_elephant.tga
texture seleucid, data/models_unit/textures/mount_african_elephant_seleucid.tga
texture parthia, data/models_unit/textures/mount_african_elephant_parthia.tga
texture merc, data/models_unit/textures/mount_african_elephant_mercenary.tga
model_flexi data/models_unit/mount_elephant_african_400.CAS, 15
model_flexi data/models_unit/mount_elephant_african_300.CAS, 30
model_flexi data/models_unit/mount_elephant_african_200.CAS, 60
model_flexi data/models_unit/mount_elephant_african_100.CAS, 80
model_flexi data/models_unit/mount_elephant_african_70.CAS, max
model_tri 700, 0.3f, 0.3f, 0.3f

You can provide 'thrace,' line for texture selecting whichever existing tga is most appropriate. If you don't add in the 'thrace' lines it will generally just default to one of the others (not necesarily the one you wanted) - the thing that actually crashes game is if you specify file path to a tga / dds that doesn't exist.