It depends to some extent on which way the fence faces, but in any case I would suggest a border of perennial geraniums (not the bright red or pink sort that you see in tubs) They are mostly shades of blue or pink, some like shade and some are happy in full sun. They grow to various sizes. Some quite tall and flop over to cover a large area in summer. some hug the ground and stay small, some hug the ground and wind in and out of other plants.. Some flower more or less all summer and some have a much shorter season. Some die back completely in winter so you can put spring bulbs very close to them.

You haven't said where you live - if you are within reach of a good nursery you could see what they have. Long Acre Plants have a good selection- they specialise in plants that do well in shade so if this applies to you that might be a good place to look - try telling them what colour, height and spread you are after.

If your border is wide enough you might like to consider something taller for variety, or perhaps a climber to go on a or wires fixed to the fence?

I'm sure there will be lots of other useful suggestions.

I think that Steragram has hit upon the right approach with Geranium...
I have a thing for them, so will always encourage others to get to enjoy their delights.
Might I suggest - Geranium Nodosum
Fits in well just about anywhere and seeds freely.

Just avoid Geranium x oxonianum! That is a thug. :-(

But if you sadly want to ignore Spritzhenry's advice I can gladly give you as many as you want....I started with one six years ago and now have lost count.

I like the shrubby Euonymus, emerald 'ngold and emerald gaiety they are so easy to look after, not much pest or disease, give a bit of height to the border and look bright and cheerful whatever tne weather, lovely foil for the pretty hardy geraniums

Oh Steragram - there are so many better-behaved beauties than the thuggy one. Yes, it's useful to fill spaces, and the flowers are pretty, but it can take over, as I know to my cost. :-(

I'm using it to keep back a wild bank behind it which it does very well, but it does get around doesn't it? (The one plant I started with was given to me before I knew what it was like... I have a huge tall blue one there as well that grows very tall and then flops over so it does tend to take over though it doesn't run. - don't know what it is, any suggestions? It does disappear altogether in winter though, which isn't ideal in that particular spot.Rozanne is doing a bit of a take over bid too - I can't resist the blue ones and I wish I wasn't too idle to keep the labels! Always think I'll remember, but of course it never works out that way.

How huge is huge? Does it have rather brittle 'joints'?

I suspect it's 'Spinners'. I cut mine back hard after flowering and it obliges again later. :-) I have to put plant supports in it, as it does indeed 'flop'.

Rozanne has gone mad this year - much wider 'clumps' than in previous years!

Its about two feet tall and then flops over all the way round. Last year I remembered to put hazel twigs round it which helped but didn't do it this year.I'm going to put some photos on later and one one of these on of the geraniums in question geraniums is right at the back of the shot of the new bed I made last autumn. I got it all wrong and it needs a big shift round in the autumn. Not a clear shot I'm afraid.

I made a comment on your photo. If you want to post another with a close-up of the leaves/flowers, I could be more confident. ;-)