there seens 2b a bug or some kind of file mismach that is making the snakes headlless
ive copy the logs so hopefully this could help

Failed to find any textures at Things/Snake/Head/ while constructing Multi(initPath=Things/Snake/Head/, color=RGBA(1.000, 0.400, 0.325, 1.000), colorTwo=RGBA(0.000, 0.000, 0.000, 0.000))
UnityEngine.StackTraceUtility:ExtractStackTrace ()
(wrapper dynamic-method) MonoMod.Utils.DynamicMethodDefinition:Verse.Log.Error_Patch1 (string)
Verse.Graphic_Multi:Init (Verse.GraphicRequest)
Verse.GraphicDatabase:GetInner<Verse.Graphic_Multi> (Verse.GraphicRequest)
AlienRace.AlienRenderTreePatches:HeadGraphicForPrefix (Verse.PawnRenderNode_Head,Verse.Pawn,Verse.Graphic&)
(wrapper dynamic-method) MonoMod.Utils.DynamicMethodDefinition:Verse.PawnRenderNode_Head.GraphicFor_Patch2 (Verse.PawnRenderNode_Head,Verse.Pawn)
Verse.PawnRenderNode/<GraphicsFor>d__67:MoveNext ()
Verse.PawnRenderNode:EnsureMaterialsInitialized ()
Verse.PawnRenderNode:EnsureInitialized (Verse.PawnRenderFlags)
Verse.PawnRenderNode:EnsureInitialized (Verse.PawnRenderFlags)
(wrapper dynamic-method) MonoMod.Utils.DynamicMethodDefinition:Verse.PawnRenderTree.EnsureInitialized_Patch1 (Verse.PawnRenderTree,Verse.PawnRenderFlags)
Verse.PawnRenderer:RenderCache (Verse.Rot4,single,UnityEngine.Vector3,bool,bool,bool,bool,System.Collections.Generic.IReadOnlyDictionary`2<RimWorld.Apparel, UnityEngine.Color>,System.Nullable`1<UnityEngine.Color>,bool)
RimWorld.PawnCacheRenderer:OnPostRender ()
(wrapper dynamic-method) MonoMod.Utils.DynamicMethodDefinition:RimWorld.PawnCacheRenderer.RenderPawn_Patch1 (RimWorld.PawnCacheRenderer,Verse.Pawn,UnityEngine.RenderTexture,UnityEngine.Vector3,single,single,Verse.Rot4,bool,bool,bool,bool,UnityEngine.Vector3,System.Collections.Generic.IReadOnlyDictionary`2<RimWorld.Apparel, UnityEngine.Color>,System.Nullable`1<UnityEngine.Color>,bool)
RimWorld.PortraitsCache/PortraitParams:RenderPortrait (Verse.Pawn,UnityEngine.RenderTexture)
RimWorld.PortraitsCache:Get (Verse.Pawn,UnityEngine.Vector2,Verse.Rot4,UnityEngine.Vector3,single,bool,bool,bool,bool,System.Collections.Generic.IReadOnlyDictionary`2<RimWorld.Apparel, UnityEngine.Color>,System.Nullable`1<UnityEngine.Color>,bool,System.Nullable`1<Verse.PawnHealthState>)
(wrapper dynamic-method) MonoMod.Utils.DynamicMethodDefinition:RimWorld.ColonistBarColonistDrawer.DrawColonist_Patch1 (RimWorld.ColonistBarColonistDrawer,UnityEngine.Rect,Verse.Pawn,Verse.Map,bool,bool)
RimWorld.ColonistBar:ColonistBarOnGUI ()
RimWorld.MapInterface:MapInterfaceOnGUI_BeforeMainTabs ()
(wrapper dynamic-method) MonoMod.Utils.DynamicMethodDefinition:RimWorld.UIRoot_Play.UIRootOnGUI_Patch2 (RimWorld.UIRoot_Play)
(wrapper dynamic-method) MonoMod.Utils.DynamicMethodDefinition:Verse.Root.OnGUI_Patch2 (Verse.Root)