Ok. The field is a bit over lit. Change the light decay from none to quadratic, which closer simulates how light dies. As light travels it loses intensity, if the decay rate is set to none, then the light will not be natural.
Shadows would also help the scene out. You can try using depth map shadows, with the Dmap Filter set to about 3, setting the Dmap Filter to a higher level than one softens the shadows around the edges.
(My wife just told me she thinks your field is Cool
For the Lights, I believe that they are spot lights, you should try increasing the Penubra which will soften the edges of the lights as well. At the moment the edges are too sharp. I believe you can see the effect that it will have on the light in the Light Shape box. Soft light edges occur in real life, the amount depends on the light and the distance.
To import a file texture, you can go to the attribute editor, ctrl-a,
go to the material node/tab. There you will see a little checkered box next to the different attributes. Click the box, select file from the next menu- Click on the folder icon next to image and navigate to the folder with the image.
I believe that you have a good start. Sorry I got to run, I'll finish writing tomorrow
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