I’ve made a previous topic about my start in the lucid experiences trying to figure out what it is I experience: [new to this, what am I experiencing?)
anyway, I can only get “images” to appear, not to last. as soon as I see something, I sort of focus with my eyes to look at it, and it slowly dissapears. 
I fight to keep it but then I already lost mental focus on the dreaming itself. I try not to do that but I do unintentially. is there anything particular to do not to ruin it all the time? its very frustrating. its like watching a movie but the tv turns it self off so you have to walk up and put it on again. over and over.
I have a similar problem. I’ve been working with my imagery at night before I fall asleep. The few times I have created an image in my head, I get startled, jump and then lose the image.
Like last night, I saw a very clear 3D image of a moving, chocolate colored laboradore retriever puppy. He was moving and everything. I couldn’t believe I had created that image in my head and litterally jumped. I can’t figure out why it startled me so much!
Anyone have any advice for us??
that is exactly what I do! often the images are 2 dimentional at first, like watching tv. it is when i start to loose focus I see the “depth” in it. and it seems to be totally random what I see. once I saw a mans torso, wearing a black tshirt. and yesterday i saw a sign of some sort with some warning or something. can’t remember exactly but it looked like the “warning - explosive” sign on a webpage or something.