Basic test for images within SVG, as described here with a tool to generate the SVGs here. Comment to report any oddities with specific browsers.

External SVG with data URI assets via <img /> tag
Not working in Safari 8 or iOS7 Safari

External SVG with Data URI as background-image,
Not working in Safari 8

Inline SVG with data URI assets

External SVG with external assets via <img /> tag
Not working in Chrome, Firefox, Safari or iOS7 Safari. Probably a cross-domain issue.

External SVG with external assets as background-image,
Not working in Chrome, Firefox, Safari or iOS7 Safari Probably a cross-domain issue.

SVG encoded as Data URI with external assets as background-image,
Not working in Chrome, Firefox, Safari or iOS7 Safari Probably a cross-domain issue.

Inline SVG with external assets

Inline SVG with external <use> of the external assets SVG.