Some excellent recommendations here that should be addressed.
However, in Hoster 4.0x, there is a setting you may need to adjust.
1. Run Hoster
2. Click the Tools menu > Show Display... command
3. Click the Lyrics view first, and change the
Position: field to "Stretched".
4. Do this for Intermissions, Audio DJ and Video VJ (if they all allow changing it).
Click Apply, and see the changes, or close and see them.
We shipped the "default state" as Centered, which would not "resize" your graphic image, but left it in exactly the aspect and resolution it was created in. Shifting to Stretched will allow your image to resize automatically.