This is actually a common issue that I see popup every once in a while. You want to load in your images using SDL_image (or just SDL), but you then need to turn that surface into an OpenGL texture. It's actually quite easy:
GLuint TextureID = 0;

// You should probably use CSurface::OnLoad ... ;)
//-- and make sure the Surface pointer is good!
SDL_Surface* Surface = IMG_Load("someimage.jpg");

glGenTextures(1, &TextureID);
glBindTexture(GL_TEXTURE_2D, TextureID);

int Mode = GL_RGB;

if(Surface->format->BytesPerPixel == 4) {
    Mode = GL_RGBA;
}

glTexImage2D(GL_TEXTURE_2D, 0, Mode, Surface->w, Surface->h, 0, Mode, GL_UNSIGNED_BYTE, Surface->pixels);

glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

//Any other glTex* stuff here
Your texture is now ready to be used. Be sure that GL_TEXTURE_2D is enabled.

Render example:
glBindTexture(GL_TEXTURE_2D, TextureID);

// For Ortho mode, of course
int X = 0;
int Y = 0;
int Width = 100;
int Height = 100;

glBegin(GL_QUADS);
    glTexCoord2f(0, 0); glVertex3f(X, Y, 0);
    glTexCoord2f(1, 0); glVertex3f(X + Width, Y, 0);
    glTexCoord2f(1, 1); glVertex3f(X + Width, Y + Height, 0);
    glTexCoord2f(0, 1); glVertex3f(X, Y + Height, 0);
glEnd();