In my experience, I encountered a similar issue in Firefox 39.0 where images would disappear completely when using
filter: url("data:image/svg+xml;utf8,<svg xmlns=\'http://www.w3.org/2000/svg\'><filter id=\'grayscale\'><feColorMatrix type=\'matrix\' values=\'0.3333 0.3333 0.3333 0 0 0.3333 0.3333 0.3333 0 0 0.3333 0.3333 0.3333 0 0 0 0 0 1 0\'/></filter></svg>#grayscale"); /* Firefox 3.5+ */
To resolve this issue, I found that adding "filter: grayscale(1)" fixed it:
filter: url("data:image/svg+xml;utf8,<svg xmlns=\'http://www.w3.org/2000/svg\'><filter id=\'grayscale\'><feColorMatrix type=\'matrix\' values=\'0.3333 0.3333 0.3333 0 0 0.3333 0.3333 0.3333 0 0 0.3333 0.3333 0.3333 0 0 0 0 0 1 0\'/></filter></svg>#grayscale"); /* Firefox 10+, Firefox on Android */
filter: gray; /* IE6-9 */
filter: grayscale(1); /* Firefox 39 (and above? Don´t know) */
-webkit-filter: grayscale(100%); /* Chrome 19+, Safari 6+, Safari 6+ iOS */
This solution worked for me. I have not tested it on IE 10+ yet.