2048x2048x16/32 = 6,7108,864/134,217,728 bits ;) Which is around 17mbs.

GAH! Forgot to logon. Well the 10mb was a quick caluculation, off with 50% quite bad :P.

Well, anyway. I did my math, and I'll be fine with 1 maximumly 2 2048's. and that's 32mb videomemory. + Like nothing for my vertexbuffer etc. Might even fit it all on a 64mb vram card.

Thanks for all advices. Still open for sugestions, and still wondering if 2048 is bad in any other way than being large. And if all gfx cards has atlas op?

I don't think any video card knows about atlas textures. Actually I'm 99.999% sure they don't. It's pointless it's a technique programmers came up with to speed things up.

Since even a Riva TNT 2 supports 2048² textures, I´d say you´re fine using them. But I wouldn´t limit your 2D game engine to use just one of these. According to your posts your tiles are 128x64 in size, which gives 512 tiles per 2048 textures max. If you´re going to include some animations somewhere that isn´t that much.
So, if you´re going to add support for more than one texture, which you should I´d say, there´s nothing keeping you from trying out whether there is a performance bonus when using 4 1024² textures or even 16 512² textures instead of one 2048² texture.
But I guess you´ll be fine with 2048² textures.