How To Associate Default App Icons With Files?

[spode2]

I am using Lubuntu 14.04 and I have replaced the bundled media players with just SMplayer. I have changed the default settings and if I double click on a media file SMplayer opens as it should. The file properties show SMplayer as the default app.

How can I get the appropriate file types to display the SMplayer icon, rather than just a blank?

[spode2]

The problem seems to be that the file manager does not recognise .ts files as video. If I change the file type to .mpg I immediately get a video icon. So which file tells PCManFM what icon to apply?