On total there is 65 non-store mounts available. There are certain, which are ones that you need to "choose" from and those are Winterlight Solstice mounts Percht Sleigh. There are three available to choose from: Cold, Bright and Dark. I'm not 100% if you can only have of those, or more. There's option to upgrade each of those to "variant" and "finished" ones and there is the choice you need to make: to keep basic version or variant/finished. If you want some additional reading check out links below. According to feedback here you can have every and each 9 of them, so I updated my answer. So there aren't any more in my mind which you need to choose from.
https://tibia.fandom.com/wiki/Mounts?so=search
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