Ive been playing a bit with shaders and 2D tints and managed to compile 2 of them.

I post it here in case it could be useful for anyone or even me in the future.

for sepia tint just use this

uniform sampler2D image;

void main() {

vec3 texel = texture2D(image, gl_TexCoord[0].xy).rgb;

gl_FragColor = vec4(texel.x,texel.y,texel.z, 1.0);

gl_FragColor.r = dot(texel, vec3(.393, .769, .189));

gl_FragColor.g = dot(texel, vec3(.349, .686, .168));

gl_FragColor.b = dot(texel, vec3(.272, .534, .131));

}

For a Black & white filter this one

uniform sampler2D image;

void main() {

vec3 texel = texture2D(image, gl_TexCoord[0].xy).rgb;

gl_FragColor = vec4(texel.x,texel.y,texel.z, 1.0);

gl_FragColor = max(texel.r,max(texel.g,texel.b));

}