diff --git a/packages/maps/preview/readme.txt b/packages/maps/preview/readme.txt
index d97dcc7a..29cb8152 100644
--- a/packages/maps/preview/readme.txt
+++ b/packages/maps/preview/readme.txt
@@ -1,3 +1,7 @@
-Place preview pictures of custom maps into this directory.
-Reduce the image size to ~200x150 pixel.
-Do not use preview pictures, if you're already low on graphics memory.
+Place preview pictures of your custom maps into this directory.
+Requirements:
+ * The image size must be a maximum of 200x150 pixels.
+ * It must be in JPEG format (with a lower-case ".jpg" extension).
+
+Do NOT use preview pictures, if you're already low on graphics memory.
+You can disable them by using the command "hidebigmenuimages 1".