Love in the air... LoL... I love it... Spaceranger & Drivenslush are among the loveliest, este, I mean, among the most helpful souls in PXL...

Author, ur in good hands! Good job and good luck!!!

Well author, take three jars of peanut butter, rub them on your cat, then run around the back yard naked and scream "Wubba Wubba Wubba" at the top of your lungs. All the time remembering when your older brother ate the last piece of cake even when Mom SPECIFICALLY told him that YOU should get the last piece. I think that's how you do it.
J/K
Just go to your profile drop down, Click the "My Entries" link and there should be a big green square block next to your entry that says REPLACE IMAGE, click it and you should be able to upload your new image. It will take a second and your updated image will appear. (Hiding from Spaceranger before the Thunks me)

Drivenslush is quite right, you have plenty of time to improve your entry no reason to wait for the next contest. A shadow will make a big difference in your entry and they aren't hard to make. You can see from the car the shadow would be directly under the tractor, simple to do just give it a try. You can find many tutorials with tips on shadows, this one is very good and you'll find others listed on the same page: https://www.youtube.com/watch?v=ft5TP0taDJU

Beginner McShinner.. we all start some where and improvements can be made right up to the point before voting ensues. You have 14 days so if you think of something that will improve the image I say go for it It's perfectly okay to leave it as is as well. As my big brother would say, "No big Whoop."

Fun idea author... some suggestions, I can see you blurred the tractor a bit, you should then blur the doggy as well to get them to match up visually.. (Low Res Image is hard to see). Also, you may want to think about placing a shadow of some sort under the Tractor do ground it. At this time it looks like the Tractor is floating or cut and paste which isn't a bad thing, but in competition it will trounce you in the voting.
Good luck and welcome to pxleyes.