Whenever you use the <img> tag, you are specifing the location of a file, not the actual image content.
You won't be able to use <img> unless you save it to a file. Vice versa, you won't be able to output the image unless you display nothing else.
First, base64_decode the image:
$image = base64_decode($image);
Now, you have two choices: do you want to save it to a file and <img> it, or do you want to output it to the browser?
Saving it to a file:
$imfp = fopen("file.gif","w+b");
fputs($image);
fclose($imfp);
echo("<img src=\"file.gif\">");
Output it:
header("Content-type: image/gif");
echo($image);
Hope this helps.