The skybox IDs are defined inside the main stage table: Levels at the struct value of 0x8. Skybox's are a combination of several different layers of graphics, and each part can be scaled differently. It seems different combinations of those effects are used and composted into a single skybox ID, creating many multples. When the skybox doesn't completely cover the background, you can use the struct value 0xA in the main stage table to give a background color. It is not currently known how to combine the original graphics together into a single background.

1. 0x0: 'USE 0xA color ID',
2. 0x1: 'White Molding Pattern',
3. 0x2: 'Green Hills w/ Clouds 1',
4. 0x3: 'Green Hills w/ Clouds 2',
5. 0x4: 'Green Hills w/ Clouds 3',
6. 0x5: 'Green Hills w/ Clouds 4',
7. 0x6: 'Green Hills w/ Clouds 5',
8. 0x7: 'Orange Tree Leaves Narrow',
9. 0x8: 'Green Hills w/ Clouds 6',
10. 0x9: 'Green Hills w/ Clouds 7 (Broken)',
11. 0xA: 'Trees Blue Mosaic Sky 1',
12. 0xB: 'Trees Blue Mosaic Sky 2',
13. 0xC: 'Blue Mosaic Sky',
14. 0xD: 'Large Trees Yellow BG'
15. 0xE: 'Sand Dunes Blue Sky 1',
16. 0xF: 'Sand Dunes Blue Sky 2',
17. 0x10: 'Blue Sky Gradient 1',
18. 0x11: 'Sand Dunes Blue Sky 3,
19. 0x12: 'Ice Mountains Light Blue Sky 1',
20. 0x13: 'Ice Mountains Light Blue Sky 2',
21. 0x14: 'Sand Dunes Blue Sky Clouds',
22. 0x15: 'Blue Sky Clouds 1',
23. 0x16: 'Blue Sky Clouds 2',
24. 0x17: 'Yellow BG Dark Holes',
25. 0x18: 'Above Clouds Light Blue Sky 1',
26. 0x19: 'Above Clouds Light Blue Sky 2',
27. 0x1A: 'Green Tree Tops 1',
28. 0X1B: 'Just Tree Trunks',
29. 0x1C: 'Green Tree Tops 2',
30. 0x1D: 'Green Tree Tops 3',
31. 0x1E: 'Green Tree Tops and Tree Trunks',
32. 0x1F: 'Scrolling Clouds Blue Sky 1',
33. 0x20: 'Scrolling Clouds Blue Sky 2',
34. 0x21: 'Scrolling Clouds Blue Sky 3',
35. 0x22: 'Scrolling Clouds Blue Sky 4',
36. 0x23: 'Purple Blue Sky Gradient 1',
37. 0x24: 'Purple Blue Sky Gradient 2',
38. 0x25: 'USE 0xA color ID',
39. 0x26: 'Scrolling Clouds USE 0xA color ID 1',
40. 0x27: 'Scrolling Clouds USE 0xA color ID 1',
41. 0x28: 'USE 0xA color ID',
42. 0x29: 'Palm Trees USE 0xA color ID',
43. 0x2A: 'USE 0xA color ID',
44. 0x2B: 'Tree Trunks Jungle Foliage',
45. 0x2C: 'Static Clouds 1',
46. 0x2D: 'Static Clouds 2',
47. 0x2E: 'Static Clouds 3',
48. 0x2F: 'Static Clouds 4',
49. 0x30: 'Static Clouds 5',
50. 0x31: 'Red Sky Gradient 1',
51. 0x32: 'Grey Sky Gradient 1',
52. 0x33: 'Grey Sky Gradient 2',
53. 0x34: 'USE 0xA color ID',
54. 0x35: 'Grey Sky Gradient 3',
55. 0x36: 'Scrolling Eggs USE 0xA color ID 1',
56. 0x37: 'USE 0xA color ID',
57. 0x38: 'Scrolling Eggs USE 0xA color ID 2',
58. 0x39: 'USE 0xA color ID',
59. 0x3A: 'Scrolling Blue Eggs USE 0xA color ID',
60. 0x3B: 'Scrolling Eggs USE 0xA color ID 3',
61. 0x3C: 'Colorful Blocks and Hills 1',
62. 0x3D: 'Colorful Blocks and Hills 2',
63. 0x3E: 'Colorful Blocks and Hills 3',
64. 0x3F: 'Grey Sky Gradient 4',
65. 0x40: 'Black w/ MM vignette gfx',
66. 0x41: 'Purple w/ Silhouette Skyscrapers'
67. 0x42: 'Yellow Gradient Green Hills w/ Paint Doodles 1'
68. 0x43: 'Yellow Gradient Green Hills w/ Paint Doodles 2'
69. 0x44: 'Yellow Gradient Green Hills w/ Paint Doodles 3'
70. 0x45: 'Yellow Gradient Green Hills w/ Paint Doodles 4'
71. 0x46: 'Black w/ Dark Blue Spook Clouds'
72. 0x47: 'Black w/ Vert Scrolling Dark Red Spook Clouds'
73. 0x48: 'Demo Blue Checkerboard'
74. 0x49: 'Crash'