You could do what TikTok13 suggested, but there's also another way. For Pokemon between Gens 1 and 5, you can use the national Pokedex number of the Pokemon you wish to have a Sprite of surrounded by either a : or ; symbol, depending on the generation. Gens 1-4 use the ; symbol and Gen 5 uses the : symbol. For example:
I want to have Pokemon number 403, I would put a ; symbol, followed by the number 403, then another ; symbol. Like this:
;403;
Whereas if I want Pokemon number 621, I would put a : symbol, followed by the number 621, then another : symbol. Like this:
:621:
I hope I helped! (Tip: if you're still unclear, click "Reply With Quote" so my text pops up in the text box and you can see how the code works more thouroughly. To quite the Reply With Quote function, simply click Cancel.)