Render only the first image (of a sequence) as thumbnail

Hello,

i would like to ask the following question:

I have a sequence of images, which should be displayed by an image gallery. The image gallery plugin normally generates for everey image a corresponding thumbnail.
Is there a way to customize the plugin, so that only the first image of the seqence is shown by a thumbnail (the other images should only be visible by traversing the gallery).

Thanks in adavance,

Michael

-- MichaelSchmid - 24 Dec 2015