Ember loading substate and images/css animation rendering

I have a route in my Ember App which returns a promise and it takes some time to do that, so I decided to create a loading substate and it works fine except for the images and the spin loader (css animation) present in the loading substate template:

• Static Images take a while to render especially on mobile and IE where sometimes they don't show at all
• The CSS animation spin loader gets stuck while transitioning to the actual route and again on mobile sometimes it doesn't show at all.

What could be a solution to show a loading substate static template that is very smooth and that, once the model has been loaded, it disappears without any lag/freeze of my css animation or slow rendering of my images?

We are talking about 5 very small images...

Thanks guys