Use base64-encoded SVG for Firefox.

static/styles/amarr.css

@@ -19,5 +19,5 @@ a:hover {
 }
 
 #campaigns-select {
-    background-image: url('data:image/svg+xml;utf8,<?xml version="1.0" standalone="no"?><svg height="60" width="60" version="1.1" xmlns="http://www.w3.org/2000/svg"><polygon points="13,20 48,20 30,45" style="fill:#584A26;"/></svg>');
+    background-image: url('data:image/svg+xml;base64,PD94bWwgdmVyc2lvbj0iMS4wIiBzdGFuZGFsb25lPSJubyI/PjxzdmcgaGVpZ2h0PSI2MCIgd2lkdGg9IjYwIiB2ZXJzaW9uPSIxLjEiIHhtbG5zPSJodHRwOi8vd3d3LnczLm9yZy8yMDAwL3N2ZyI+PHBvbHlnb24gcG9pbnRzPSIxMywyMCA0OCwyMCAzMCw0NSIgc3R5bGU9ImZpbGw6IzU4NEEyNjsiLz48L3N2Zz4K');
 }

static/styles/caldari.css

@@ -19,5 +19,5 @@ a:hover {
 }
 
 #campaigns-select {
-    background-image: url('data:image/svg+xml;utf8,<?xml version="1.0" standalone="no"?><svg height="60" width="60" version="1.1" xmlns="http://www.w3.org/2000/svg"><polygon points="13,20 48,20 30,45" style="fill:#364A5F;"/></svg>');
+    background-image: url('data:image/svg+xml;base64,PD94bWwgdmVyc2lvbj0iMS4wIiBzdGFuZGFsb25lPSJubyI/PjxzdmcgaGVpZ2h0PSI2MCIgd2lkdGg9IjYwIiB2ZXJzaW9uPSIxLjEiIHhtbG5zPSJodHRwOi8vd3d3LnczLm9yZy8yMDAwL3N2ZyI+PHBvbHlnb24gcG9pbnRzPSIxMywyMCA0OCwyMCAzMCw0NSIgc3R5bGU9ImZpbGw6IzM2NEE1RjsiLz48L3N2Zz4K');
 }

static/styles/gallente.css

@@ -19,5 +19,5 @@ a:hover {
 }
 
 #campaigns-select {
-    background-image: url('data:image/svg+xml;utf8,<?xml version="1.0" standalone="no"?><svg height="60" width="60" version="1.1" xmlns="http://www.w3.org/2000/svg"><polygon points="13,20 48,20 30,45" style="fill:#284A36;"/></svg>');
+    background-image: url('data:image/svg+xml;base64,PD94bWwgdmVyc2lvbj0iMS4wIiBzdGFuZGFsb25lPSJubyI/PjxzdmcgaGVpZ2h0PSI2MCIgd2lkdGg9IjYwIiB2ZXJzaW9uPSIxLjEiIHhtbG5zPSJodHRwOi8vd3d3LnczLm9yZy8yMDAwL3N2ZyI+PHBvbHlnb24gcG9pbnRzPSIxMywyMCA0OCwyMCAzMCw0NSIgc3R5bGU9ImZpbGw6IzI4NEEzNjsiLz48L3N2Zz4K');
 }

static/styles/minmatar.css

@@ -19,5 +19,5 @@ a:hover {
 }
 
 #campaigns-select {
-    background-image: url('data:image/svg+xml;utf8,<?xml version="1.0" standalone="no"?><svg height="60" width="60" version="1.1" xmlns="http://www.w3.org/2000/svg"><polygon points="13,20 48,20 30,45" style="fill:#5F3632;"/></svg>');
+    background-image: url('data:image/svg+xml;base64,PD94bWwgdmVyc2lvbj0iMS4wIiBzdGFuZGFsb25lPSJubyI/PjxzdmcgaGVpZ2h0PSI2MCIgd2lkdGg9IjYwIiB2ZXJzaW9uPSIxLjEiIHhtbG5zPSJodHRwOi8vd3d3LnczLm9yZy8yMDAwL3N2ZyI+PHBvbHlnb24gcG9pbnRzPSIxMywyMCA0OCwyMCAzMCw0NSIgc3R5bGU9ImZpbGw6IzVGMzYzMjsiLz48L3N2Zz4K');
 }