Base64 encoded image does not work in iRule

I have a maintenance page that looks like this:

The sample image is base64 encoded in the HTML file. I uploaded the HTML file and made an iFile (lb-failed-html) in order to use it in the following iRule:

when LB_FAILED { 
    HTTP::respond 200 content [ifile get "/Common/lb-failed-html"]
}

But the page takes too long to load (actually it won't load). It seems to be the base64 encoded image.

Is there any way I can fix this issue? Thanks in advance