Tried out 512px tiles and sprites and they actually look like crap. They just look like bad textures not better painted. With 256 they look nicely pixelated.

assets/config.json

@@ -1,15 +1,17 @@
 {
   "textures": [
-    "assets/tile01.png",
-    "assets/tile16.png",
-    "assets/tile02.png",
-    "assets/tile03.png",
-    "assets/tile05.png",
-    "assets/tile17.png"
+    "assets/floor_tile_test-512.png",
+    "assets/wall_texture_test-512.png",
+    "assets/ceiling_test-512.png",
+    "assets/wood_wall-512.png"
   ],
   "sprites": [
-    "assets/portal.png"
+    "assets/armored_knight_1-512.png",
+    "assets/cinqueda_1-512.png",
+    "assets/wood_barrel_large-512.png",
+    "assets/evil_eye_test-512.png",
+    "assets/undead_peasant-256.png"
   ],
-  "floor": "assets/tile32.png",
-  "ceiling": "assets/tile10.png"
+  "floor": "assets/floor_tile_test-512.png",
+  "ceiling": "assets/ceiling_test-512.png"
 }