I think it is the combinations of pieces. The first two outfits seem to have a knit, tee substitute top, and the longer less fitted boyfriend cardis plus the casual flat boots really make the looks casual, although the skirt itself could probably be dressed up for a casual wedding.
The next two with the blue pencil are still suffering casual boot and cardi syndrome. Plus, the fabric of the blue pencil looks casual in these pictures, but it could be the wrinkles. However, if the fabric wrinkles easy, it will wrinkle sitting at he wedding. The two silk blouses are nice, but they aren't enough to dress up the other pieces.
I can see the blouse in pic three with a jacket or black or colored cardi belted (or a more cropped, fitted style), with a black or colored pencil more similar to the halogen skirt or with the black and white skirt in number 1, with tights and black pumps. A dress with a jacket would be a good look-- if it seems too black, a scarf would go a long way. I'm sorry, I'm blanking on what you have to play with at the moment.
The look in 3 would probably be great with a non bf sweater topper and different shoes. If it will be warm inside the church (enough for the short sleeves) I'd just wear my dress jacket over it, skip the cardi, and wear a pair of pumps or any other "dressier" black shoes with the tights. I think the blouse in 3 is slightly dressier by itself than the blouse in 4, but I don't think the sleeve length looks as dressy or as flattering with your IT shape.