After researching, I found the answer to my own question.
FTP transfer isn't able to display thumbnails unless it downloads the file and then generates one. It seems that on a couple of applications the programers have found a way to generate a thumbnail without downloading the entire file first although it's not very fast.
I used a file application called 'FileBrowser' that seemed to display thumbnails without downloading first but I was wrong. The application I mentioned downloads a file the first time you access it and then holds the thumbnail on the Ipad until your maximum is reached and then drops the older ones. What that does is make for instant access of thumbnails. You can set the number pf thumbnails stored from 1,000 up to 10,000. By storing previously accessed file thumbnails you essentially have them for instant access. A very good way around the FTP thumbnail issue.
I like thumbnails of jpg's, pdf's and documents. Photo icons are absolutely necessary, especially if you don't rename every photo. I have couple of websites I maintain and now a Synology NAS in the house that I'm setting up. I'm also using a couple of cloud services that in honesty I may drop when I figure out the NAS better.
My problem is with thumbnails on the Ipad. In some applications I can see image thumbnails and in others I don't. Thumbnail representations most always show up if it's on the Ipad but when accessing the NAS or a remote ftp,, on some apps, photo thumbnails just show an icon with jpg, pdf or other on a box.. Dropbox jpg images show up in their app but may not in others. There is a file app, 'Filebrowser' that shows my Synology jpg and PDF icons as photos (wonderful) but a favorite file app of mine, 'Ifiles' which I want to use as my primary file app doesn't. (terrible) Drives me a bit crazy.
This post is really a rant. I just don't understand why there is so much inconformity it's like plumbing.
Is there something I may not be doing to cause this or is it just programing (or sloppy programing) and I need to deal with it.
Thanks for any input.