Updated social preview image.

index.html

@@ -10,12 +10,12 @@
     <meta property="og:type" content="website" />
     <meta property="og:site_name" content="WebVM"/>
     <meta property="og:url" content="/">
-    <meta property="og:image" content="https://webvm.io/assets/webvm.jpeg" />
+    <meta property="og:image" content="https://webvm.io/assets/webvm_preview.png" />
     <meta name="twitter:card" content="summary" />
     <meta name="twitter:site" content="@leaningtech" />
     <meta name="twitter:title" content="WebVM" />
     <meta name="twitter:description" content="Welcome to WebVM - a server-less virtual Linux environment running fully client-side in HTML5/WebAssembly.">
-    <meta name="twitter:image" content="https://webvm.io/assets/webvm.jpeg" />
+    <meta name="twitter:image" content="https://webvm.io/assets/webvm_preview.png" />
     
     <!-- Apple iOS web clip compatibility tags -->
     <meta name="viewport" content="width=device-width, initial-scale=1" />