Swapping out the protagonist's sprite with my own

[Espeon]

I just started getting into spriting and have been working on a custom character (see link below; still looking for feedback, advice, tips, ... btw ;) ).

 So, my question is: in my sprite I added some type of psychic shield on which my character is standing/surfing. For the overworld sprite, I thought if would be nice to copy the surfboard from Rejuvenation's character Kieran. However, I'm not sure whether it'd have the same effect since I don't know whether Rejuvenation's creators added something in the code to make Kieran move like he does (I dont' know how any of this works under the hood). If it'd require modifying the code, I'm not going to go through with adding the psychic shield into the overworld sprite, because I would definitely break the game meddling with the code. If, however, I can get my character to move like Kieran just by editing the images, I'd love to do that. Could anyone help me figure this out?

 

I also cannot find the files of Kieran moving sideways (left and right), only up and down (Characters folder, trchar_125_1), so if anyone knows where they are - if, that is, they exist in the first place (I haven't found any footage in which he travels sideways, hope it's a coincidence) - please let me know.