diff --git a/Makefile b/Makefile
index 3b3d046..35e6952 100644
--- a/Makefile
+++ b/Makefile
@@ -1,6 +1,7 @@
 
 release:
-	mkdir pkg && \
+	mkdir -p pkg && \
+		rm ./pkg/*.zip && \
 		git archive --prefix=graftorio2/ -o pkg/graftorio2_0.0.8.zip HEAD
 
 install-darwin:
diff --git a/thumbnail.png b/thumbnail.png
new file mode 100644
index 0000000..013c8cb
Binary files /dev/null and b/thumbnail.png differ