This is a very nice mod. I really like the new decorations it adds. The Aquarium is probably my favourite one! I also really like that some of these decorations are very complex.
I have a couple of suggestions to make the mod even better.
1. All the placeables in the base game use the Swing useStyle. Some of the placeables in your mod use a different one. I think that should be changed for consistency.
2. I think all the placeable versions of existing items should be crafted on a Heavy Workbench. Also, the word "Placeable" should be changed to "Decorative". All if these changes are needed for consistency with decorative potions and a repaired life crystal from the 1.4.4.
3. It would've been cool if the pottery version of a Rubblemaker was one of the options that you can get by right-clicking it similarly to how you switch sizes of rubble. If that's hard to do, maybe the item should look different not to resemble the Rubblemaker to prevent requests like this one.
4. I've found out that you can attach Wall Vines to a nearby block without needing a wall behind it. Not sure if it's intentional or not since Wall Flowers don't have this ability.
5. I know it's a strange question, but why does a Lawn Candy Cane produce light? Sure, you can turn it off using wires, but why does something made of candy produce light in the first place?
6. I think some items should have better names. Right now some different items have similar names and some names are just slightly weird.
Here are my ideas:
Potted Christmas Tree Snowy -> Potted Snowy Christmas Tree;
Horizontal Book Stacked -> Horizontal Stacked Books;
Easter Egg -> Colorful Easter Egg;
Easter Egg (Single Color) -> Easter Egg;
Lectern with Book -> Lectern with a Book;
Rubblemaker Pottery -> Rubblemaker (Pottery);
Plants should also have different names, but I'm not too sure how to call them.
7. Right now the mod requires Shop Expander to get certain items. This is the case with the Santa Claus NPC. He has only one free slot in the base game and this mod adds 3 items to it. Besides, Santa Clause can only arrive in hardmode and I think these items can be obtained in a different way, solving both problems:
1) Paintable Light is obtained by throwing any Christmas Light into the Shimmer. Makes sense since your version is superior (Shimmer gave it the power).
2) Snowman is craftable using snow and some other things. Waiting until hardmode just to place a Snowman is a bit too rough anyway.
3) Lawn Candy Cane is craftable from Candy Cane Blocks. This is a logical recipe that will also make this item obtainable earlier in the game.
Also, the Painter sells this mod's items in both of his shops. Not sure if you can do something about it, but it'd be nice if they were only sold in the "Decor" shop.
8. I think rather than adding a Lectern with a Book item, what if you allowed people to right-click Lectern while holding a Book to place a book on it and right-click without holding a book to get it back? It'd be pretty original.
9. I think some sprites do need some tweaks. For example, paint bottles, a globe, a hospital bed or easter eggs. The palettes and the shading on those could be improved. Also, would be nice if a Skeleton Model used Skeleton's palette. Sure it is meant to look artificial, but this change would make it usable in more types of builds (it would fit well in a haunted house build, for example).
10. Lastly, I have a couple of mod compatibility suggestions.
1) Could you, please, make a Rubblemaker place Blood Chamber Pots (from Thorium mod) once it's ported to 1.4.4? They would consume Bloodstained Blocks.
2) Consolaria mod implemets the St. Patric's Day. Would be cool if Bags o' Green dropped from enemies then. Easter Bags could drop from Lepus as well. They wouldn't be decraftable using Shimmer until hardmode to prevent getting Pixie Dust in pre-hardmode. It's not really a suggestion, just something for you to think about.
By the way, shouldn't there be an apostrophe before the letter "s" in the name (shouldn't the mod be called Dragon's Decorative Mod)?
I hope you'll find my feedback helpful. Good luck!