Ok here's a quick write-up. This is a simple way to add a picture as a texture. Building coned surfaces in sketchup is not easy so I wont go into building a sub for now. You just have to play with circles alot.
1. Find a picture of the item you want in your model. I use
sonicelectronix site for this as they have NICE big multiple pictures. They do place their logo in every pic but its not that obtrusive. In any case save it to your drive.
2. Load up Sketchup and Draw a simple box.
3. Click the paint bucket to open up the material browser
4. Click the Create Button to open up the Mix New Material Box
Here is where all the magic starts
5. Click the little folder in the middle right to open up the File dialog box. From here browse to where you saved the picture/texture you got.
6. Move over to the box you drew ealier and paint it with the bucket tool
7. Here you see some issues. Mainly it's not scaled properly. To fix that you have to modify the dialog box for the texture. Make note of how I changed the numbers so that It fills more of the box in.
8. Now that the texture fills most of the box in, Draw a line where you want to cut the texture off. Delete every line past that line
9. Your amp is looking better now, But its not 3D Nor is it to scale. Fix that with the push/pull tool first. Worry about scale later.
10. Now one of the most important steps when dealing with textures. highlight the entire box and make it into a Group. If you skip this, then the box/amps texture will shift whenever you move/scale the box. By making it a group the program will automatically scale the texture along with the box
11. The final step is scaling it to proper size. I took the measurements from SonicElectronixs.com and scaled the box down to that size.
By doing this I could then move the amp around, twirl it, twist, put it on the side of a box, do anything I want with it and see how'd it look before actually touching the box/amp.