System background images in tate mode

[cskitch]

Normal/horizontal system background images are incorrectly displayed in tate mode.

e.g. I have created a 320w x 240h background image named arcade.png and a 240w x 320h named arcade_tate.png

The skin is available here - https://cdn.discordapp.com/attachments/596620993657700352/714471969122287626/Speedball.zip

You can see in this screen recording at the end (1m27s) that it appears arcade.png is being displayed instead of arcade_tate.png https://drive.google.com/file/d/1BwvHNK8e9LSY2Jn1Pt1M132YDI1n132d/view?usp=sharing