Hi,
Having looked at your pictures, I can see that you have actually put some thought into the background when you took your pictures, and they don't look bad. In fact compared to some of the pictures on ebay, they are pretty good, but they can be improved some more.
You are right in that the actual colour of the fence is fairly neutral, in fact some photo editing programs have grey as an option when editing. The problem is that it is not a uniform single colour, it is pattened and that makes your plants somewhat blend in. While grey is neutral, white is generally considered better, especially when photographing something that has shades of white in it, so that people can see how much it differs to white.
I have included 2 pictures of the cheap **bleep**py light box I made out of some cardboard boxes, a white LED light and some plain cardboard sheets. Ignore the fact that I break a cardinal rule about white backgrounds, I'm going for a theme for my store. I do still have a white sheet that I use when I really need it, like my cream coloured high heels.
The purple cardboard goes from horizontal to vertical with a curve, rather than at right angles, this makes it very hard to tell where the floor ends and the wall begins. What that means is that the background falls away and you focus just on the object.
The reason I use a big long light is that the light hits the object from several different directions at once which minimises shadows, if I had used something like a desk lamp, that has a single point of light, there would be a big shadow on the other side of the object. I should also stick some white paper to the boxes I am using as a light stand, because when the light bounces of the brown cardboard, the light gets a little browner than it should be. Also, having white surfaces for the light to reflect off would further reduce the shadow problem,
Obviously this type of thing is only good for your smaller plants, but for your bigger ones, you might want to try a big clean white sheet and sow a dozen fishing sinkers to each of 2 ends of the sheet. you could then hang it over the fence without it easily blowing away. Also, take your pics in the morning before the wind picks up.
