I assume you have Itunes? If you dont. You need it.
Ok, I have an Ipod, Ipod Mini and Ipod Video. I dont have the Nano but the process' your asking about should be the same as the Ipod Video.
1) Pictures - Create a file. Give it a name. Add all the photos you want to it. Then go to itunes. Right click the ipod icon on the left hand side (only there when ipod connected) Go to the 'ipod' tab. Then the 'photos' tab. Tick the 'Synchronise photos from' box, but be sure to choose the folder you created from the drop down box next to it..you will have to browse for the folder. Its done. When adding photos in the future, it will either be just add them to the folder you created or - within your folder, itunes will have created a 'cache' folder...this is normal, you may have to add the new photos here...not sure..trial and error I am afraid as I have not tried yet.
2) Pictures - Album/single artwork - Double click the song you want to add artwork too. So it knows what song you want to add too. In the bottom left hand corner of i tunes, yu will see a square box saying something like 'drag artwork here' Do exactly as it says. To delete it, just right click the song in itunes and click 'get info' click the tab that says 'artwork' and follow the instructions.
Note: To update your ipod with artwork I have to do the following: Go to your ipod icon on the left hand side, right click, go to 'ipod options' click the 'ipod' tab. At the bottom you will see a tick box saying "Display album artwork on your ipod" If is already ticked, unclick it, press 'ok' go back to that same point and this time re-tick the box and again click 'ok' If it was unticked you need to just tick the box. This must be done every time you want to update. Its a quick process once you know how.