hi def backgrounds are reduced in size

Hello Everybody. This is my first post on this forum and I thank all who will help me out with a problem I'm having. I created my own background theme for my desktop and it worked well until I did a couple system updates. Now, the backgrounds scroll every 10 seconds and still have nice, crisp detail, but the image is appearing as 'zoomed in'. I tried to reset the desktop settings so that the JPEGs are set to 'Fill' the entire screen, but it still only shows about half of the background.
On the same note, I am curious if using a variety of resolution sizes are hard on my processor/graphics card. I'm trying to create a custom desktop with various icon docks, skins, and backgrounds to compliment the factory color scheme my laptop came with. Any help greatly appreciated (& hope everyone is having good holidays!).

An update: I've tried (& repaired) many ideas from several techs and it is even worse now. What the H311 am I doing wrong? Before, it was cropping around 25% off (showing most- about 75%- of picture) and now it is about half. I was sure to return all settings back to the original setting before going on to try the next idea, so I'm just at a loss to understand what is causing this. Hope someone can help me.

Yes, that is my native resolution. So this is normal if I get pictures with too high a resolution? I thought (incorrectly) that 1680x945 was the minimum resolution, so the majority of pictures had more res.
I appreciate your answer and I look forward to learning so much more here on the Forum- Thanks for having me.

I see what you mean now. It sucks being a NOOB, but I’ll catch on quickly. So, I have to have images at the 1680 x 945 aspect ratio. I did what you said and ‘hovered’ over some of the files and noticed that most have been converted- but not all. I checked the link you provided and did a little research on aspect ratio and found several cool programs (I wanted PhotoShop, but couldn’t afford it) and settled on one called IrfanView. I found a simple set of directions here:
How to Stretch a Picture Without Distorting It - Resize a Photo Without Loss of Image Quality
And it converted the entire folder (211 MB) as a batch in about two minutes. I again hovered over each thumbnail and it showed that all have been converted to the 945, but not the other. Looks like it’s not going to be as easy as I’d hoped.

Well, everything worked out just fine and I started dividing up my backgrounds into seperate themes. Finished earlier today and I was very happy! I went to the bathroom and when I got back, somebody had slipped into my room and made off with my laptop. Just when I had it just the way I wanted....