So, I've been on Pixpet for a bit now and thought I'd throw in my two cents here too. Valtien already posted a very extensive list of things that I agree with but I am still going to bring up all things I thought of as well!

Pixpets and you

Currently, Pixpets is a lot about sitting around and doing nothing. I know that many here like the community effect, but I am more of the silent type (unless it is compiling a long list like this one) and would prefer to actually do things with my pets.
Hoarding is neat, but when I have to wait over a day for my pet to even show back up home, it kinda takes the fun out of it.

My Solution for this:
-People can choose a "main" pixpet that is at their side
-Main Pixpets can go on a walk with you. It could be called "Haul"
-Main Pixpets can not hoard
-On a haul, you would be presented with a grid, similar to that of your home.
-There will be different places to visit. Example: Meadow is better for green and lime pets to haul at. Beach is great for yellow and blue pets etc.
-Hauling at a place that matches your pets color will more likely give you rewards.
-You can haul at places that do not match your pets colors for rewards that do not match its color, but you are more likely to leave empty handed
-When on a haul, you click a tile. You then decide whether to "Dig", "Look" or "Sniff"
-Dig makes it more likely to find seeds/maybe grown produce (rarely)
-Look makes it more likely to find Decorations/pots/Pixcoins/Eggs
-Sniff makes it more likely to find Fertilizer/Crafting items
-Hauling has a chance of finding nothing as well
-Hauling can sometimes give you special food that you can feed to your or other pixpets to raise the SLVL (does not give rewards like lottery, but is just an act of kindness!)
-You can haul a certain amount of times, before your main pet needs a rest

Also, the possibility to pet your pet. Even if it's just a button. Maybe have it raise SLVL slightly.

Easier Crafting
Right now I have a hard time crafting, simply because I feel like it's a lot to keep track of. My solution to this:
-How many items are needed and you have are shown on the recipes.
-Clicking a recipe adds the ingredients to the pot, given you have the items in your inventory.
-Clicking on an ingredient that is craftable brings you to the recipe of said ingredient

Housing

I do not know if this is planned out yet, but what about player built housing? Houses that can be crafted and sold? Not a must, but an idea for the housing market perhaps.