diff --git a/resources/cosmetic/cosmetic.json b/resources/cosmetic/cosmetic.json
index 0aebefbbe..7f1741692 100644
--- a/resources/cosmetic/cosmetic.json
+++ b/resources/cosmetic/cosmetic.json
@@ -9,15 +9,15 @@
   },
   "pattern": {
     "stripes_v": {
-      "pattern": "ARAIBQ==",
+      "pattern": "ASQQVVU=",
       "role_group": ["all"]
     },
     "stripes_h": {
-      "pattern": "ARAIAw==",
+      "pattern": "ASQQDw8=",
       "role_group": ["all"]
     },
     "checkerboard": {
-      "pattern": "ARAICQ==",
+      "pattern": "ASQQpaU=",
       "role_group": ["all"]
     },
     "diagonal": {
diff --git a/src/client/Cosmetic.ts b/src/client/Cosmetic.ts
index 3e8987377..9b0a33c54 100644
--- a/src/client/Cosmetic.ts
+++ b/src/client/Cosmetic.ts
@@ -51,7 +51,7 @@ export class PatternDecoder {
       height > 63
     ) {
       throw new Error(
-        "Scale must be 1–128, width must be 1–127, and height must be 1–63.",
+        `Invalid pattern metadata: scale (log₂)=${scale}, width=${width}, height=${height}. Expected: scale 0–7, width 1–127, height 1–63.`,
       );
     }
 
diff --git a/src/client/TerritoryPatternsModal.ts b/src/client/TerritoryPatternsModal.ts
index 5a37f005e..8255856b0 100644
--- a/src/client/TerritoryPatternsModal.ts
+++ b/src/client/TerritoryPatternsModal.ts
@@ -219,7 +219,10 @@ export class TerritoryPatternsModal extends LitElement {
     const cellCountX = decoder.getTileWidth();
     const cellCountY = decoder.getTileHeight();
 
-    const cellSize = Math.min(height / cellCountY, width / cellCountX);
+    const cellSize =
+      cellCountX > 0 && cellCountY > 0
+        ? Math.min(height / cellCountY, width / cellCountX)
+        : 1;
 
     return html`
       <div