this was fun until 46.
the pictures for the last 5 prompts are pretty much one pixel wide.
it's so narrow you can't really make out a shape due to lack of continuity, and because of it being considered all border, it's all black so you can't even use the color as a general hint;
it's no different than having no picture at all. ended up brute-forcing them by going through the whole natdex in order.
putting the answers here for future reference:
01. swadloon
02. pupitar
03. drifblim
04. wobbuffet
05. scizor
06. druddigon
07. krokorok
08. mienshao
09. kricketot
10. torkoal
11. heracross
12. manaphy
13. carnivine
14. haxorus
15. poochyena
16. dusknoir
17. azurill
18. aggron
19. lotad
20. dustox
21. slowpoke
22. rapidash
23. eevee
24. latios
25. piloswine
26. palkia
27. dialga
28. misdreavus
29. croagunk
30. jolteon
31. zubat
32. torterra
33. meloetta
34. ampharos
35. porygon
36. omanyte
37. stoutland
38. whirlipede
39. archeops
40. gothita
41. pelipper
42. suicune
43. spinarak
44. vanillite
45. numel
46. oshawott
47. mewtwo
48. kecleon
49. magnezone
50. krookodile