How to center thumbnails in nextgen widget

+1 – same problem and I cannot find a solution

the widgets.css doesn’t help

Which widget are you talking about? The one with random images or slideshow?

with recent images (the newest images)

I can’t reproduce the issue because mine is centered. A page URL to the problem would be useful. Probably your issue is due to the area in which the widget is inserted, so try with default theme and with all plugins but Nextgen deactivated.

https://www.rcheliolomouc.cz/alba/

in the footer on the left

pictures are left aligned

Simply add in plugin custom CSS area
.ngg-widget {padding: 15px;}
(the code can be improved)
or from the widget itself enlarge images width enough to fit the space.

my theme is fully responsive – it is not a solution

I would use this css code:

.ngg-widget {
text-align:center;
margin-right:5%;
}

ok in control pannel->gallery->styles I’ve copied

.ngg-widget {
text-align:center;
margin-right:5%;
}