I appreciate the idea, and I'd definitely be willing to pay to sustain a group of artists churning out content 24/7, but there are a number of problems with your current system.
I will begin by breaking down item by item - please don't take this as an offence, I'd love for you guys to succeed and I would love to become a client.
- Ninja character: Only one attack animation, jump animation too stiff, graphic style would need to be the same in all other assets in order to make a game out of this, ninjas are too "naruto" with the headbands, there is no "classic" ninja that would be compatible. Here is a more usable ninja, though with some animation problems as well.
- Weapons/tools/items: Don't know how easy it is to change colors, style is inconsistent with the rest of the graphics (switched to pixel art instead of vector), gold looks like copper, there isn't enough differentiation. Here are some swords with more variation, though with the same problem of being hard to change colors.
- Pixel RPG Houses: Some are simply recolors or have one or two items swapped around. Why not give us individual elements so we can make our own, then? Also:
As is, someone could probably make a dating sim, but it's a stretch.
- They only have one style, modern suburbs - what about apartments, offices, a bank, park, mall, police station?
- They are inconsistent with your other RPG sets
- Premium pokemon tileset: What makes this "pokemon"? Why is there a zombie? Also, many tiles required to make this a full game are missing, since there is only one terrain type: grasslands
- Poker & Card Set: Only one you could make a game out of, though you could find many options for card faces, backgrounds, chips and table in other sites.
- Tower Defense Set: Unusable. Only 4 towers, no animations, once someone used those, all others would be called "clones" or "ripoffs". Stick to generic or reusable art, it's better to hire someone to do specific stuff.
- Public Pokemon Tileset: Again, what makes this pokemon specific? When you say things like this, it looks like you ripped them off the latest pokemon ROM.
- Soldiers: Can't move the arms up or down, as one might in a twin stick shooter. There is no "hit", "jump" or "duck" animation. Might also want some terrorists, other camo colors (green), maybe some soviet lookalikes?
- Platformer Tileset: Extremely incomplete. I could maybe make one level, but that's it. Also, it isn't properly 9-sliced, which would make the ground look blocky, rendering the smoothed corners moot.
- RPG Tileset Vector: Extremely incomplete, no animation for water, some transitions missing (earth<->cracked earth, earth<->sand, sand<->grass, etc), incompatible with your pokemon tileset.
- RPG Tile Overlays: Extremely incomplete (forest only), most elements are just recolors/repositionings, incompatible with your pokemon tileset
- RPG Item Set: Incomplete, random mishmash of items. Maybe make a collection for books, other for gems, other for magic items, other for weapons? Incompatible with your weapons/tools/items/armor pack.
Also, I noticed some items are not your own creations. Do you have authorization to sell them? Even if you do, it isn't displayed clearly. Your licensing information is also not present.
In addition, and I think this is the worst problem for your pricing scheme, it's better for me to hold off, wait for other suckers to pay, wait for you to make a ton of graphics, then pay once, download all graphics, and maybe even make a torrent somewhere - what's stopping me, and what's encouraging people to keep renewing?