better initial image URL handling

[PeterBreen]

Investigate some way of setting the initial image URL based on first direction of travel - say, if I know it's going to move right first thing, make sure it displays the imgRight instead of a static preselected image and then setting properly after the first tick.

[PeterBreen]

Downgraded to 'enhancement' - this doesn't affect function in any way other than the first 20ms of the app's lifespan. I'm still interested in fixing it, but it's not a priority compared to others.