I disagree with @Astr0Derp 's answer as there indeed appear to be hidden asset types. Here are all I’ve been able to gather from various sources including devforums and various roblox & api wikis. However, note that there at least 5 missing asset types that I could not find any where and are marked in the list as “Unknown”. Please do let me know if you discover their values at some point.
Hopefully this is of any help to you.
-- * is a guess/suggestion made by the AI
local AssetTypes = {
[1] = "Image",
[2] = "TShirt",
[3] = "Audio",
[4] = "Mesh",
[5] = "Lua",
[6] = "HTML",
[7] = "Text",
[8] = "Hat",
[9] = "Place",
[10] = "Model",
[11] = "Shirt",
[12] = "Pants",
[13] = "Decal",
-- [14] = "Unknown", -- * "VideoClip", "VideoOverlay"
-- [15] = "Unknown", -- * "Article", "Widget"
[16] = "Avatar",
[17] = "Head",
[18] = "Face",
[19] = "Gear",
-- [20] = "Unknown", -- * "Subscription", "PluginEmulator"
[21] = "Badge",
[22] = "GroupEmblem",
-- [23] = "Unknown", -- * "Bundle"
[24] = "Animation",
[25] = "Arms",
[26] = "Legs",
[27] = "Torso",
[28] = "RightArm",
[29] = "LeftArm",
[30] = "LeftLeg",
[31] = "RightLeg",
[32] = "Package",
[33] = "YouTubeVideo",
[34] = "GamePass",
[35] = "App",
-- [36] = "Unknown", -- * "Game"
[37] = "Code",
[38] = "Plugin",
[39] = "SolidModel",
[40] = "MeshPart",
[41] = "HairAccessory",
[42] = "FaceAccessory",
[43] = "NeckAccessory",
[44] = "ShoulderAccessory",
[45] = "FrontAccessory",
[46] = "BackAccessory",
[47] = "WaistAccessory",
[48] = "ClimbAnimation",
[49] = "DeathAnimation",
[50] = "FallAnimation",
[51] = "IdleAnimation",
[52] = "JumpAnimation",
[53] = "RunAnimation",
[54] = "SwimAnimation",
[55] = "WalkAnimation",
[56] = "PoseAnimation",
[57] = "EarAccessory",
[58] = "EyeAccessory",
[59] = "LocalizationTableManifest",
[60] = "LocalizationTableTranslation",
[61] = "EmoteAnimation",
[62] = "Video",
[63] = "TexturePack",
[64] = "TShirtAccessory",
[65] = "ShirtAccessory",
[66] = "PantsAccessory",
[67] = "JacketAccessory",
[68] = "SweaterAccessory",
[69] = "ShortsAccessory",
[70] = "LeftShoeAccessory",
[71] = "RightShoeAccessory",
[72] = "DressSkirtAccessory",
[73] = "FontFamily",
[74] = "FontFace",
[75] = "MeshHiddenSurfaceRemoval",
[76] = "EyebrowAccessory",
[77] = "EyelashAccessory",
[78] = "MoodAnimation",
[79] = "DynamicHead",
[80] = "CodeSnippet",
}