Any hints please? Really stuck on this one!

Yeh, it's a toughie. I'm stuck, too.

Notice that the columns and rows have identical patterning? I worked on the basis that the two had to intersect... ie. row 5 and column 5 - the 3's intersect to form a +.

There are several possible answers :/.

You Char, should be shot for this.

Use the 1s to form zigzags and diagonals. :) & Thank you Pearce.

It's symmetrical, the center is a box with a single three in the middle of each 11 and an x in the middle. Each inside corner of the box is filled in. Hope this helps but not a super intriguing image.

Thanks to Pearce, Alev, Rats-eijnah

In addition:
- all 3's form +'s
- all 1's connect only to 1's

So many possible solutions X_X.

Thank you!

Really there are lot of possibilities. The right one is based in zig-zag.

Could someone provide more hints? Possibly actual row/column values? I'm not finding any zig-zags.

Couldn't see the zigzags until the puzzle was finished, haha.
Thank you for the hints Rats-eijnah & LeeAtari.

I think pearce's clue is deceptive--the 3s in C5 don't match up with the 3s in R5; R5 pairs with C9 and C17.