How to put specific shapes/textures instead of generating colors (C#)

Hello,

My problem is that I'm making pentomino-like game and I'm generating shapes from matrixes. Code works well, etc. But my problem is to add textures to them (2D plant-shape like figures). Is there any method to hardcode them or is this just wrong from the beginning and I should start with different approach and models of that pentominos?

Right now:

     public void InitBlockTextures(int w, int h) //initializing block textures
     {
         green_texture = new Texture2D(w, h);
         ...
         black_texture = new Texture2D(w, h);
         CreateBeveledTexture(green_texture, 0, 1, 0);
         ...
         CreateBeveledTexture(black_texture, 0, 0, 0);
     }
 
     public Texture2D GetBlockTexture(int color) //for each color we're getting texture
     {
         if(color==1)return green_texture;
         ...
         if(color==8)return black_texture;
         return null;
     }

I used matrixes and colors generated that way cause it was pretty simple to program rotating options for something like this:

 public class PentominoPieces //here we have pieces
 {
 ...
     int[,] P8R1 = new int[4,4]    {
         {1,1,0,0},
         {0,1,1,0},
         {0,0,1,0},
         {0,0,0,0}
     };
 ...
 }

 public int[,] GetTetrisPieceBitmask(int type, int rotation) //each rotation has specified bitmask
 {
     ...
     if(type==8)
     {
         if(rotation==1)return P8R1;
         if(rotation==2)return P8R2;
         if(rotation==3)return P8R3;
         if(rotation==4)return P8R4;
     }

 

But now it not looks that easy anymore and I'll be thankful for every help.