well... of course you can use them... it's always possible. The way XP designed there scripts is so that it reads the rectangles.
1 is going to be Idle then it moves in a 1,2,3,4;1,2,3,4 going from left to right. and no matter how big the rectangle is it's always going to move in that order. So the sprite you have up there should work just fine.
but the screen is only 640 by 480 pixels so using bigger sprites might take up too much space. alwase try to make your sprites small, but big enough to keep all the details that you want
also... if you want to make tile sets bigger you cant just expand it 2x bigger because it has to have a 256 width or else It would only show half of the tileset when you try to lay it down.
If you dont see what I mean try it and I'm sure you'll see the problem.
there is a way to fix this. but it would be just more time consuming. make it 2x bigger than take the extra 256 pixels on the right and bring them down to the bottom. so your tileset will still be 256 pixels wide but it will be 2 times longer...
but if you really are willing to put in the effort to make your game more "pixelated look" then go ahead, it's your game
But you said the other reason is because your not good at spriting. If you want Im really good at it.

I'll be glad to make you any sprites you want. sprites, battlers, sideview battlers, title, gameover, animation, tilesets, autotiles, battlebacks, icons, faces... anything else I couldn't think of off the top of my mind...

just PM me if you need anything =)