All you need to make your own resources in iso !
This is an iso at 22 degree like in the GTBS .
First , use the following TileA5 to map the ground :
(https://rmrk.net/proxy.php?request=http%3A%2F%2Fi89.servimg.com%2Fu%2Ff89%2F11%2F59%2F23%2F52%2Ftilea511.png&hash=cfb1a8bed0744c248a582b98e4c5076f8d75f29f) (http://www.servimg.com/image_preview.php?i=62&u=11592352)
Then use TileB-E for other stuffs .
This is the template :
(https://rmrk.net/proxy.php?request=http%3A%2F%2Fi89.servimg.com%2Fu%2Ff89%2F11%2F59%2F23%2F52%2Ffond10.png&hash=bd447442c64a61c66f28c1ba4798284785af62f8) (http://www.servimg.com/image_preview.php?i=63&u=11592352)
And with this template , i made this :
(https://rmrk.net/proxy.php?request=http%3A%2F%2Fi89.servimg.com%2Fu%2Ff89%2F11%2F59%2F23%2F52%2Fisovil10.png&hash=ee48e1e8f3132dfc252cb627a2a55e5d4d97cfc3) (http://www.servimg.com/image_preview.php?i=59&u=11592352)
in-game result :
(https://rmrk.net/proxy.php?request=http%3A%2F%2Fi89.servimg.com%2Fu%2Ff89%2F11%2F59%2F23%2F52%2Fiso_vi10.png&hash=9f527d8255b9ae4d2b86c77056350924fd14ed8a) (http://www.servimg.com/image_preview.php?i=66&u=11592352)