If your images are not rendering check you php memory_limit settings. Magento doesn't support the "1G" notation. Apply this fix to your sources:

gistfile1.diff

Index: lib/Varien/Image/Adapter/Gd2.php
===================================================================
--- lib/Varien/Image/Adapter/Gd2.php  (revision 143037)
+++ lib/Varien/Image/Adapter/Gd2.php	(revision 143038)
@@ -82,7 +82,9 @@
      */
     protected function _convertToByte($memoryValue)
     {
-        if (stripos($memoryValue, 'M') !== false) {
+        if (stripos($memoryValue, 'G') !== false) {
+            return (int)$memoryValue * 1024 * 1024 * 1024;
+        } elseif (stripos($memoryValue, 'M') !== false) {
             return (int)$memoryValue * 1024 * 1024;
         } elseif (stripos($memoryValue, 'KB') !== false) {
             return (int)$memoryValue * 1024;